Many child victims of trafficking are not getting the help they need because social workers fail to recognise the signs, a charity says.
Lack of communication hampers information about trafficking
Researchers from the charity, End Child Prostitution and Trafficking (ECPAT), interviewed social workers in 33 London boroughs.
They concluded the majority of social workers in the region were not being given the training and resources to help trafficked children.
Caron Somerset of ECPAT - a coalition comprising several UK child agencies including UNICEF and the NSPCC - said their study showed many cases may slip through the net.
"Many of the social workers we interviewed for the report felt that they may have missed cases of trafficking through not being aware of this issue," she said.
Workers in 26 of the 33 boroughs surveyed said they had concerns about the circumstances in which a child had been brought into the UK or was living, Ms Somerset said.
'Lack of communication'
However, there is no guidance for child protection workers about what trafficking is or what they should do if they are suspicious, Ms Somerset added.
"Without guidance, practice manuals and safe accommodation for trafficked children, the protection of those children and the prevention of trafficking will continue to be an almost impossible task," she said.
The report found that children trafficked from African, eastern Europe and parts of Asia were most likely to end up in London.
East European children were most likely to be trafficked for sexual purposes while more than half of trafficked African children ended up as domestic "slaves", the report found.
Thirty-five cases were documented in the boroughs surveyed.
However, a lack of communication between boroughs and sometimes even within teams meant it was hard to establish the scale of the problem in London, Ms Somerset said.
"To find out all cases of child trafficking in London, a researcher would need to be able to speak to each and every individual social worker."