The findings suggest that when trafficked children try to escape from imprisonment in Britain, their cries for help are ignored or negligently handled by UK agencies. The report, by the Children's Society charity, found that those who managed to escape their captors were often returned to domestic imprisonment, where they were forced to work as prostitutes in brothels or as slaves in British homes. Children who were allowed to leave their guardian's home were usually too frightened to disclose what was happening to them.
One young girl trafficked to Britain was groomed and sexually exploited while in the care of children's services. She did not know that what was happening was illegal, or that it was considered abuse.
The United Kingdom Human Trafficking Centre (UKHTC) is aware of 325 children from 52 countries who may have been trafficked in 2008. But the Children's Society, which looked closely at 46 cases in the UK, said these figures did not account for young people who feel they have no choice but to keep their ordeals a secret.
More than half of the young people in these initial case studies had attended school while in Britain, but when they asked for support from various agencies, the frontline workers did not know how to help or refer them. The charity said that some who had reported their situation found frontline workers unwilling to help, disbelieving the seriousness of their claims or unaware of where to refer them.
Even when a child is identified as being at risk of exploitation and taken into care, they still face kidnapping by traffickers. In May this year, it was discovered that 77 children had gone missing from a single children's home near Heathrow since March 2006. It is estimated that 1.2 million children worldwide are trafficked each year, in a trade worth £16bn annually.
"Whilst recent media reports have claimed that the problem of trafficking has been overstated, this new research brings into startling perspective the very real problems faced by children separated from their carers and exploited and mistreated by those responsible for them in the UK," said the authors of the report.
The study's disturbing findings will add to growing pressure on the Government to introduce a law making domestic servitude and forced labour an offence in the UK for the first time. Last week, ministers backed down and dropped opposition to a new anti-slavery offence punishable by 14 years' imprisonment. Some of the children living on the streets of the world's poorest cities are picked up by criminal gangs before being sold on to traffickers who take them to countries including Britain. Others are sold to traffickers by their parents. The most common countries of origin are China, Vietnam, Bangladesh, India, Afghanistan and Nigeria.
Lisa Nandy, policy adviser for the Children's Society, said: "Whilst sexual exploitation may be the most high-profile form of trafficking, young people can be, and have been, exploited in a number of different ways, including forced labour and domestic servitude. All of these children are extremely vulnerable, and the agencies need to work together to identify and support these victims."
The 46 children's journeys to Britain varied greatly but most came from Asia and Africa. Many of them arrived by plane and either with the person they would be living with, a family member or a trafficker. Some entered undetected on lorries or trucks and one reported coming by boat.
Some came to join family members in the UK, but in nearly every case the children were brought into the country on other people's passports and by people claiming to be their parents.
One girl was told to wear boy's clothes and memorise a new identity. She said she "messed up" her answers to the immigration official who questioned her, but this was not picked up and she ended up imprisoned in a British home.
From Africa to slavery: 'They shouted at me, hit me and beat me'
*Anna, 16, was brought to Britain from Africa by a woman who told her mother she would find her daughter a good home and a better life in London.
She was one of six women and children on the flight who were being escorted by the woman. On arrival in the UK, the girls were taken to a van and driven around the city, being dropped off at various locations.
A woman who was to be Anna's guardian paid the trafficker some money and Anna was handed over to her new mistress. She lived with a married couple who had a young son. Her duties involved rising at 6am to do some cleaning before waking the couple's son, giving him breakfast and making him lunch. She then cleaned until 12pm and went to her bedroom until it was time to pick the boy up from school.
When they got home, Anna helped him with his homework, cooked and did other chores until 9pm when she went to bed. The woman would often call her to get out of bed to do more chores, such as fetching and carrying drinks and snacks for the family. "If I didn't hear her call, she would come upstairs and pour cold water on my face in bed," Anna said.
"The woman shouted at me, hit and beat me for things like not knowing that she had finished her cup of tea. The beatings increased over time. The woman also sent me to clean the houses of several of her friends."
Eventually, Anna was befriended by a woman whom she met at the school gates. She was initially suspicious that the woman's kindness was not "genuine", and thought that if she went to her she would be kicked out on to the street. But in the end, she decided to ask her for help.
When Anna and her new guardian tried to find her a place at a local school, they were told nothing could be done because she had no identification papers. Finally, the new guardian decided to hand her over to the police.
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