More needs to be done to raise awareness about Britons being trafficked abroad with special emphasis on trafficking in children, according to European experts.
The claim is made by GRETA (Group of Experts on Action against Trafficking in Human Beings) in a report on how well British authorities have implemented the Council of Europe Convention on Action against Trafficking.
The report is the first assessment of how well the nation has responded to signing up to agreements in 2007 with a British strategy covering the period 2011 to 2015.
GRETA said it welcomed "the awareness-raising measures already taken" and noted "that the measures to discourage demand have so far focused on sexual exploitation".
But it called for more work to be done to stop people being trafficked for slavery.
The experts said they were concerned by reports that "a significant number" of children in care go missing.
More needs to be done to identify child trafficking victims, the group said, and to ensure all unaccompanied minors who are potential victims of trafficking are assigned a legal guardian and are provided with suitable safe accommodation and adequately trained supervisors or foster parents.
Responding to reports that potential trafficking victims are detained in immigration detention centres, police cells or prisons, the authors set out steps to help officials establish if someone has been trafficked.
GRETA applauded the authorities for securing funding to deal with the issue during straitened times but called for more help supporting people with their recovery, employment and education.
The study identified British devolution as a problem with different legal and institutional approaches to human trafficking.
GRETA said the authorities should consider "the consequences of having numerous pieces of legislation".
The experts also called for the authorities to "step up their efforts to adopt a victim-centred approach" and that potential trafficking victims should not be punished for immigration-related offences.
Klara Skrivankova, Anti-Slavery International's anti-trafficking programme co-ordinator, said: "GRETA's report has recognised many of the concerns raised by NGOs(non-governmental organisations) over the past three years, in particular warnings that victims of trafficking are being prosecuted for offences committed as a consequence of being trafficked.
"Anti-Slavery International supports recommendations to review the current focus on immigration that can sometimes preclude preventing trafficking victims from being properly identified and protected.
"We echo the concern that the system introduced to identify and protect those trafficked, known as national referral mechanism, currently seems to favour victims from within the EU over those outside of the EU, despite the requirement to treat all victims of trafficking equally.
"We also support GRETA's recommendation that the British authorities adopt measures to guarantee access to compensation for victims of trafficking.
"Not only is the current lack of compensation preventing many trafficked people from rebuilding their lives and gaining a sense of justice, but it also means that we are losing the battle with the criminals."