Thousands of black African children are disappearing every year in the UK as they shuttled between distant relatives and used either for fraudulent benefit claims or as a source of child labour, child welfare campaigners said today.

The claim was made after police investigating the murder of a child whose torso was found in the River Thames four years ago said that 300 African boys had disappeared without trace from London schools in the three-month period leading up to his death.

The headless and limbless body, named Adam by police, was found in the river near Tower Bridge in September 2001. Police suspect he was the victim of a ritual killing after being brought to Britain from Nigeria.

To try to identify the body, the victim of a suspected ritualistic killing, Metropolitan Police officers asked every education authority in London how many black boys aged between four and seven had gone missing. In the three-month period between July and September 2001 - leading up to the killing - some 300 children were found to have disappeared.

There was nothing to suggest that they had been murdered, but a lack of immigration records made it impossible to trace them.

Tests suggest the boy, believed to have been aged between four and six and to have been alive when he arrived in London, may have been poisoned. Traces of the highly poisonous calabar bean was found in Adam’s lower intestine, and police think that may have been used to subdue him before his deat.

Other contents in his stomach including crushed bone, and clay pellets impregnated with gold and quartz were discovered in his lower intestine.

Child welfare experts fear that many African children are brought into the country for the purposes of benefit fraud, passed between adults and, in the worst cases, physically and sexually abused.

Detective Chief Inspector Will O’Reilly told the BBC Radio 4 Today programme: "We were really looking at black children, black male children, aged between four and seven. And we found 300 of those that couldn’t be accounted for. It was one of the lines of inquiry we had to follow up.

"In the main these were African children. I think there were one or two from the Caribbean."

The children’s so-called carers often told police that the youngsters had returned to Africa. Mr O’Reilly added: "When we had information that they had left the country, we asked through Interpol for police to make inquiries in the local countries to which they [were said to have] returned. In the majority of cases, we got no reply on that.

"It is a large figure, far more than we anticipated when we started this line of inquiry."

Police managed to trace only two of the 300 missing children.

Welfare groups said the case of the missing children - and the fact that thousands more may have disappeared since then around the country - highlighted the need for tightening up the rules on "private fostering", where children are placed with distant relatives or family friends. At the moment, there is no legal obligation for carers to register with their local authority.

The British Association for Adoption and Fostering (BAAF) said in a statement: "There are concerns that the number of boys and girls of all ages that go missing each year would total several thousand."

Felicity Collier, the BAAF chief executive, said that was sure that most of the missing children would be safe and well, but their disappearance needed to be investigated.

She called for legislation governing private fostering to be tightened up so that carers are obliged to register with their local authority if they were looking after a child who was not in their immediate family.

"If all private foster carers were registered and it was illegal not to register we would have a better chance of tracing children who disappear," she said.

"The sad reality is that many children come into this country and are moved around either to avoid immigration controls, or because their parents have arranged for them to live with strangers or distant relatives virtually unknown to them in the belief they will have 'a better life' in this country.

"However, others undoubtedly are exploiting these children perhaps for monetary gain through the benefit system or as domestic servants."

Theresa May, the Conservative spokesman on family issues, said: "We argued very strongly when the new Children’s Bill was going through the House of Commons that there should be a registration system and there should be a requirement on people who are privately fostering in this way to register with the local authorities.

"At the moment the onus is on the local authorities to search them out. We think the onus should be the other way around."

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