By Ben Ando BBC News The problem of young British girls being lured into prostitution is to be investigated by the Home Office. Among the victims was 13-year-old Emma.
When she first fell in with a gang it seemed great.
Emma had a new boyfriend who gave her jewellery and mobile phones, took her for drives and gave her alcohol and cannabis.
It seemed the height of teenage rebellion, but she did not realise the "gifts" were a way of controlling her.
After a few weeks, Emma was introduced by her boyfriend to some older men.
It was quickly made clear she was expected to have sex with them.
"I don't think you realise until it's too late what's really happening. When you're only 13 and a child you don't see danger like you do when you're older," Emma said.
Soon Emma was spending all her time with the older "cousins", "friends" and "uncles".
A parent's story She said: "There was one older man in particular who started to groom me and I used to have to do what he said or he'd hit me and stuff.
"It got so I'd have to go and meet him or they'd threaten to bomb the house or kidnap me.
"I was so scared it got to where I felt it was better that I go and meet him even if I knew he was going to rape me."
Emma's involvement with the gang lasted a year and during that time she estimates she had sex with dozens of men.
She also says she was not the youngest girl involved.
"I saw several other girls when I was in the flats used by the men. The youngest I saw was probably ten." 'Flattered' Emma feels she and the others were picked on because they were easy targets.
She said: "They always choose vulnerable girls.
"Obviously if you're streetwise you'll pick up on it, but if you're a bit sheltered and they buy you little things or take you to McDonalds when you're 12 or 13, then you're flattered by it because you're getting attention off someone.
"You feel as though they're your friend. They have nice clothes, nice cars, they're well groomed, so it looks as though they've got money." Tackling 'internal trafficking' Once under the men's control, she found it hard to break away.
"You've got no self-esteem or self-respect because they take that away from you.
"For someone to rape you [again and again] doesn't hurt as much as when they raped you the first time because you haven't got anything anyway. You feel that sex means nothing," she said.
'Starting from scratch' Emma's experiences have affected her badly. It has taken her many hours of counselling to realise what happened was not her fault.
"I had depression for a long time. I was on medication and didn't want to go out of the house, didn't trust anybody. I always felt physically ill. I had no confidence or anything.
"It's like starting from scratch again."
No-one has ever been prosecuted in connection with what happened to Emma.
She is trying to get on with her life, but feels cheated of her youth.
"I was a straight-A student at school. All that changed. It took away my chance of getting A-levels and going to university.
"It took away my teenage years. I never had a teenage life."
We have changed Emma's name to protect her identity.
Girls are threatened and isolated from their families
The scale of the problem of British girls being lured into prostitution in their own country is being examined by the Home Office.
A working group is being set up to examine "internal trafficking" of girls in their teens or younger.
In some cases, girls as young as 10 are believed to have been groomed by youths pretending to be boyfriends. They are passed on and end up in prostitution.
Campaigners said the authorities had been slow to react to the problem.
In a report seen by the BBC, the Home Office recommends that "the newly formed UK Internal Trafficking Group will seek to define the extent and nature of this phenomenon".
Home Office Minister Vernon Coaker confirmed it had commissioned work to examine internal trafficking.
He said a film was also being made to be shown in schools to warn children of the dangers.
"There's work going on with prosecuting authorities to make sure they're aware of this issue and understand it and then there's work going on in communities to make sure that people are aware of this as a potential problem," he said.
"We also want to have services that protect and support victims as well."
Threats and beatings The BBC has learned that internal trafficking follows a typical pattern in which a girl aged about 12 is approached and won over by a good-looking, well-dressed teenage boy.
He gives her jewellery, mobile phones and later drink or drugs, and pretends to be her boyfriend.
"Emma" told the BBC she was groomed by a teenage boy
Once under his spell, the girl is turned against her parents and persuaded to have sex with her boyfriend's older "uncles" or "friends" to pay him back for the money he has spent on her.
Gradually, she finds herself spending all her time with the older men who force her, often with violence, to work as a prostitute.
Meanwhile, her original "boyfriend" is out targeting another young girl.
One victim Emma, which is not her real name, was targeted when she was 13.
"In schools we're always warned about a man in a white van, but we're never warned that someone nearly your own age could be targeting you to groom you for prostitution," she said.
Emma was too terrified to ask for help.
"They've threatened to rape my mum and make me watch," she said.
"Firebomb my house. Shoot me, shoot my family. They've threatened to do all sorts of things."
Parents 'bewildered' Hilary Willmer, from the Coalition for the Removal of Pimping (Crop), said she had seen dozens of cases of internal trafficking.
Ms Willmer said: "It can happen to any child from any family. The men, the gangs have all the experience. The children, the families and the parents are bewildered, don't know what's happening."
She welcomed the Home Office action, but said part of the problem was the law.
Once older than 13, a girl may be asked to give evidence in court against an attacker.
"In practice, unless the primary victim is prepared to give evidence then it's very difficult to make charges stick," Ms Willmer said.
"The men know this, so they often wait until the girls are 13 before actually having sex with them."
North Yorkshire Chief Constable Grahame Maxwell said many forces were aware of this problem and officers were now trying to piece together the national picture.
He said: "It is a very difficult crime to detect. We are talking about people who don't want to talk about things in the open.
"When they actually find out the extent to which the exploitation has been carried out on them, how much they have been abused, how much they've been forced to have sexual partners, it's a very difficult thing to comes to terms with."
The UK Human Trafficking Centre (UKHTC) in Sheffield recently appointed a dedicated detective sergeant to work on internal trafficking cases.
Nick Kinsella, head of the UKHTC, said the scale of the problem was unclear.
"The whole issue with trafficking is that it's a secret, covert crime and there's a great deal of control placed over the victims and so that's always difficult to break down irrespective of the age," he said.
Thousands of women are forced to work in the sex trade
The 2012 London Olympics could become a magnet for human traffickers bringing in prostitutes and illegal workers, the government has said.
The Home Office has unveiled plans to combat gangs who imprison women and force them into the sex trade and push men into forced labour.
The UK will allow freed victims to stay for at least 30 days for counselling.
Police Minister Vernon Coaker said human trafficking was "a form of modern-day slavery".
'Exploitation' The Home Office's action plan says: "There is little doubt that there will be many who will seek to prosper from the Olympics being held in London.
"Hospitality, catering and construction workers will be required. Criminal elements are expected to exploit the situation by establishing themselves in London from now on."
An influx of young male sports fans, such as happened during the 2006 World Cup in Germany, could see a rise in demand for prostitutes, it adds.
The government has signed a European convention giving human trafficking victims more time to recover from their ordeal before deciding whether to help police.
The latest Home Office figures, from 2003, suggest at least 4,000 women from abroad have been forced into prostitution.
Mr Coaker said: "Frankly it brings tears to your eyes. It simply cannot carry on."
'Rape prosecutions' He said prostitutes' clients could face prosecution for rape: "If we have got a situation where a man knowingly has sex with a woman he knows is not freely consenting to that, then I think that that could be considered as rape."
The Home Office action plan calls for specialist trafficking teams to be set up at UK ports and airports.
It is also planning to set up an advice line for police, immigration staff and social workers and a national system to identify victims more quickly.
According to reports, "slave auctions" are being staged on the concourses of British airports.
Grahame Maxwell, of the UK Human Trafficking Centre, said information programmes were in place in countries like Bulgaria and Romania to prevent people being conned into going abroad.
One woman, imprisoned and forced to be a prostitute, had been raped 50 times on Christmas Day, the home office report said.
Another had been beaten to death after being held as a domestic slave and made to live in an outhouse, where she suffered from trench foot - caused by damp and wet conditions.
Prices Being forced to have sex 30 times a day was common, Mr Maxwell said.
He added: "The average price for a trafficked woman is £2,000 to £3,000, but up to £8,000 is reported in some cases.
"We are talking about people here. These are prices that are being paid for individuals.
"There was £8,000 charged for two 15-year-old virgins from Lithuania."
Mr Coaker said trafficked children detected at Heathrow had started "kicking and screaming because they don't believe the police officer is trying to help them.
"They've been so deceived that if they don't get there will be big consequences."
Criminals had threatened to harm their families at home if they escaped, the government said.
The decision to sign up to the European agreement has cross-party backing.
Shadow home secretary David Davis said it was necessary for "moral reasons", such as protecting exploited victims, some of whom are forced to have sex with up to 40 men a day.
Liberal Democrat leader Sir Menzies Campbell said: "Slavery still exists in the UK and we must tackle modern-day slavery wherever we find it.
"The terrible reality is that women and children are falling victim to human trafficking."
There were an 4,000 victims of trafficking working in prostitution in the UK during 2003, according to Home Office estimates.
There is evidence of thousands of children working in the sex trade
Young women tricked into coming to England, often by boyfriends, are being sold off in auctions at airport coffee shops as soon as they arrive.
They are among the thousands of women brought into the UK to be sex slaves, usually with no idea of their fate.
The trade was one of the findings of a BBC News website investigation into slavery in 21st Century England.
As the UK marks 200 years since the Parliamentary Act to abolish the slave trade, slavery goes on in another form.
The slave trade, outlawed by legislation introduced in March 1807, saw people from Africa transported en masse to the Americas with the involvement of people from the UK and other European countries.
Women rescued Modern day victims of slavery are often young women from eastern Europe, thinking they are coming to England to work as cleaners or au pairs, only to be forced into prostitution.
The Home Office estimated in 2003 that 4,000 women were trafficked into the UK for sexual exploitation. It is thought the figure may have grown since.
Police forces from Cornwall to Northumbria have found themselves having to rescue women and prosecute the traffickers who brought them to England to work as sex slaves.
And as well as foreign citizens coming to the UK, charity workers in Manchester told the BBC they believed British women working in massage parlours had been sold abroad, because they owed the owners money.
Child protection organisations and human rights groups also believe there are thousands of child sex slaves in the UK.
The UK Human Trafficking Centre was opened last year to co-ordinate the law-enforcement approach to the problem.
A spokesman told the BBC women were sometimes sold off in auctions in airport coffee shops and restaurants as they arrived in the country.
And he said there were also many cases of English women, from backgrounds of poverty, being sold from town to town to work as prostitutes.
But it is now believed that as many as 85% of women working in brothels in the UK have come from overseas - in the mid-1990s, an estimated 85% were UK citizens.
Operation Pentameter, a Home Office initiative aimed at rescuing sex workers held against their will carried out between January and July 2006, saw 84 trafficked women rescued, including 12 aged 14 to 17.
Some 230 arrests were made and more than £250,000 in cash was seized - but officers were only able to visit about 10% of the estimated number of sex establishments in the country.
'Horrific brutality' The Poppy Project, a London-based scheme which provides accommodation and support for the women, has had 581 victims referred to it since its launch in 2003.
Its own research in 2004 found evidence of "off street" prostitution in every one of London's 33 boroughs, again with the overwhelming majority of workers in brothels, saunas and massage parlours being non-British nationals.
The Helen Bamber Foundation, set up to help victims of torture and other human rights violations, said women being forced into sex slavery in England were experiencing "horrific brutality", with physical violence and the psychological trauma of being forced into sex.
The man who owned me beat me and then sold me on - I was too much trouble Jiera, 19-year-old Lithuanian trafficking victim
Many women rescued from the sex trade have said they were sold, or strongly encouraged into heading for the UK, by boyfriends or family members.
Many think they are coming to work in jobs such as cleaning or ice cream selling.
Jiera, a 19-year-old from Lithuania who was helped by the Poppy Project, thought she was coming to London on holiday with friends, only to find they were people traffickers who sold her into prostitution.
She said: "When I was with clients I tried to pretend I was doing something else, but I couldn't. It made me so angry that I was often violent towards the clients.
'Devastating effect' "The man who owned me beat me and then sold me on. I was too much trouble.
"Even if my friends don't judge me for what happened, they will always know what I did. They will never forget, and neither can I."
Many police forces - and not only in major metropolitan areas - have set up specific teams to deal with the problem.
It is estimated 85% of UK brothel workers are from overseas
Sussex Police appointed a detective to lead investigations into sexual exploitation in November.
They said they had responded to information concerning potentially exploited women working in brothels in the county almost every week since.
The government prioritised human trafficking during the UK's presidency of the EU in 2005.
In the next few weeks it is to lay out a strategy to counter the problem.
A Home Office spokesman said: "Human trafficking is a particularly horrible crime, based on deceit, exploitation and very often brutality.
"It is a crime that has a devastating effect on the lives of individuals, and contributes to the overall harm caused to the country by organised crime.
"It is important for all countries, including the UK, to do whatever is necessary to develop effective enforcement, prevention and victim support systems, both internationally and domestically."
Anna is one of an estimated 4,000 women thought to have been trafficked into the UK into a life of prostitution.
Here, she describes how she was forced to have sex and faced ice-cold baths, starvation and beatings if she did not do as she was told.
When Anna was just 12, she ran away from her home in Albania after befriending an older man.
He obtained forged papers for her and took her to Hamburg in Germany where he coerced her into prostitution.
After four years selling herself for sex, she was hidden in a lorry and trafficked into the UK where she was sold on for 2,000 Euros and employed in a brothel.
"In the beginning I was busy. I was younger and slimmer, and I was a new face," she says.
She was getting between 15 and 20 customers a day and at Christmas that could be as many as 30.
She found herself under increasing pressure to take drugs.
She tells of a time early on in her abuse when she was with one customer who had asked for two girls.
The other girl was showing her what to do but Anna started to cry when she saw the customer lying on the bed - it was the first time she had seen a naked man.
"The girl said to me to go downstairs and I went downstairs. I was crying and shouting and he [a pimp] started hitting me saying 'don't cry because you put us in trouble - why are you crying in front of a customer?'"
Icy baths Punishments were harsh and Anna was desperate to leave but too afraid to make a move.
"As soon as the bell rings I have to be ready. If they see you without make-up -'oh my god'. You are going to get hit if you don't look nice."
If she didn't make money, she would be put in a bath of ice-cold water and hit, she says.
"You are not allowed to eat if you don't make money and all the time they follow you.
"Sometimes you think you will kill yourself or try to run away. If they catch you, it's the worst thing."
Scarred by iron Eventually Anna was rescued during a police raid on the brothel.
By that stage, she was covered in scars and bruises, and permanently felt sick.
"I have got a scar, I was burned with an iron on my leg and I was beaten."
From there, she was sent to Yarl's Wood immigration removal centre before being taken in by the Poppy Project which looks after trafficked women and children who have been forced into prostitution.
She told the BBC she was recently refused the right to stay in the UK and is currently fighting attempts to send her back to Albania.
Now aged 20, she does not want to return to her home country for fear of being found and forced back into prostitution.
However, Home Secretary Jacqui Smith has said she could not give any guarantees that victims would not be deported after being rescued.