Some children do not even know they are victims themselves, says Ceop
Children who have been trafficked into the UK are being let down by the care system, a leading child protection charity has said.
Ecpat UK said many young people who are rescued from traffickers and placed in care then disappear and may end up back in the hands of criminals.
The charity is calling for victims to be appointed legal guardians.
The Home Office said approximately 360 children are trafficked into and within the UK each year.
The charity said child trafficking victims are currently put in local authority care - some with foster families, others in homes, and with 16-to-18 year olds, in the community.
But Ecpat UK figures suggest that up to 60% of children rescued from traffickers later go missing from local authority care.
And earlier this year, Prime Minister Gordon Brown promised to investigate claims that more than 80 Chinese children had gone missing from a children's home next to Heathrow airport since 2006.
Christine Beddoe, from Ecpat UK, said she wanted to see a system of guardianship introduced to ensure children get safe housing and proper support once they are rescued.
"Even in local authority care we're finding that the standard of accommodation varies so much from place to place," she said.
"Children are even being placed in bedsits located in the same area where the traffickers are. This has got to stop."
However Ecpat UK said the proposals had been rejected by the government for being too expensive.
The Home Office said the welfare of trafficked children should remain the responsibility of local authorities.
A poll for Ecpat UK and the Body Shop also found one in 10 people did not know children are trafficked into the UK.
The survey of 1,255 people suggested many Britons not only do not realise the scale of child trafficking in the UK, they may also be making it worse.
'Hard to spot'
Of those polled, 22% admitted to buying fake DVDs or visiting brothels, which can perpetuate child trafficking.
The study showed 34% of people believe trafficked children end up in foreign countries, not in Britain.
However, a government Child Exploitation and Online Protection Centre (Ceop) report in April found that victims had come to the UK from 52 different countries.
Ecpat UK said children were trafficked for domestic work or for prostitution, as well as for restaurant work and benefit fraud.
Ms Beddoe said: "Child trafficking is not easy to spot and not easy to talk about. The fact that the majority of all global trafficking is for sexual exploitation has created a taboo.
"If we are all aware, then we can all help stop children falling through the cracks in society. We can make a real difference and prevent child trafficking."
Det Insp Gordon Valentine, from the Metropolitan Police's specialist child trafficking team Paladin, said anyone using services provided by vulnerable children was "encouraging" the crime.
"If you buy off these children who are selling DVDs, especially during school hours, that must be questionable," he said.
"People who are giving to children who are begging, or people who visit brothels that are using children - these people are fuelling an awful crime.
"They are encouraging this crime and the further use of these victims and other victims that may be brought in."
Det Insp Valentine said it was common for children to be used as "criminal tools" - for example, as accomplices in cash machine thefts - and anyone with suspicions should notify Crimestoppers or their local children's services department.
"Child trafficking is very much a hidden crime, but there are opportunities for the public to notice these children that are being abused and to let us know so that something can be done," he said.
According to Ceop trafficked children themselves sometimes do not realise they are victims.
For example, some are sent away to stay with relatives on the pretext of gaining an education, but end up in domestic servitude.
The organisation said children are typically manipulated by and collaborate with the trafficker because they have been promised a better life.