Children are being trafficked from Africa and then used as sacrificial offerings in the UK, according to a leaked report commissioned by the Metropolitan Police.
The confidential report, leaked to BBC Radio 4's Today programme, also indicated that children are being beaten and even murdered because their parents and carers believe them to be possessed by evil spirits.
The report was commissioned following the death of eight-year-old Victoria Climbie, and over concerns about so-called faith crimes. The aim was to open a dialogue with Asian and African communities.
A social worker and lawyer commissioned by the police spent a year speaking to various community groups, and they compiled the report.
Excerpts from the report included: "People who are desperate will seek out witchcraft experts to cast spells for them. Members of the workshop stated that for a spell to be powerful it required a sacrifice involving a male child unblemished by circumcision.
"They allege that boy children are being trafficked into the UK for this purpose. Specific details were not forthcoming as the belief was that they would be 'dead meat' if we tell you any more."
The report also suggested that children are trafficked as domestic and sex slaves, and even for men with HIV who believe that if they have sex with a child, they will be cleansed.
The authors pointed out that these were allegations, and they could not test whether they were true.
But they voiced concerns that children could be in serious and possibly life-threatening situations.
The report also highlighted concerns about church pastors identifying children as witches, who then suffer violence at the hands of their parents.
The report says the pastors and their churches are a "lucrative business" operating throughout the UK, Europe and Africa.
It said: "A number of pastors maintain that God speaks to them and lets them know when someone is possessed ... After much debate, they acknowledged that children labelled as possessed are in danger of being beaten by their families.
"However, they would not accept that they played a major role in inciting such violence."