It is described as the new slave trade and the tragedy of human trafficking sees thousands of men, women and children disappear into an underground network of fear and intimidation they have little hope of escaping.
In some cases, child trafficking has its roots in the legitimate cultural tradition of west Africa whereby children of poor families are sent to richer relatives to gain a better education, often in return for carrying out domestic chores in the new household.
But the system has been "corrupted," according to Mr David Ould, deputy director of Anti-Slavery International, by the traffickers who act as "contractors" promising to find children work or a better life with families in other countries.
The children are often sent into prostitution or slavery to pay off the trafficking fee.
"The families take big risks and this goes together with the absolute poverty in some of these villages," says Mr Ould, whose organisation has been monitoring child slavery in the Ivory Coast. "They are told by contractors, 'I can find the child work in C⌠te d'Ivoire, or in the UK, and they could send money back home' and the children are then sent to Britain."
One of the ways in which the children arrive in Britain is as unaccompanied minors through airports. If they claim refugee status or are found to be illegal, they are transferred into the care of social services.
The social-services' centres are not detention centres, so the children have a degree of freedom to come and go. Information given to Anti-Slavery International suggests many children coming from west Africa have disappeared from the centres and in one case it is believed that a trafficker posed as a solicitor to remove a child from a social-services' centre.
Investigations into the disappearance of 66 children from the care of social services in West Sussex since 1995 have found that some of the children were carrying the telephone numbers of traffickers who they had been told to contact in Britain. Anti-Slavery International says that in some cases young girls were told during "initiation" programmes in Nigeria that traffickers were "sacred figures" who must not be crossed.
The girls were told they would be "cursed" if they did not contact trafficking gangs in Britain or other children in social-services' centres acting as go-betweens for the gangs. Some of the children were then removed from Britain by the traffickers and sent to Italy where they were put into prostitution to pay back the traffickers' fee for getting them into Europe.
Other children entering Britain from the Ivory Coast arrive with an adult who has documents that say he or she is the parent. Anti-Slavery International says there are suggestions that officials in the west African country have played a role in providing the false documents, which makes monitoring the children once they are in Britain virtually impossible.
But whereas Ireland passed a human trafficking law last year, Britain does not have identical anti-trafficking legislation. "We believe that in the short-term there is a need for legislation that will prosecute traffickers," says Mr Ould. "There is a review of all sexual offences underway. There is some discussion about the trafficking of women and within that it has been identified that a law on trafficking is needed, but it needs to be widened beyond sexual offences and prostitution."
The organisation is also calling on the British government to follow through on its commitment to stop human trafficking to give social services the power to investigate cases and establish a non-governmental organisation to provide protection for trafficked children.