Girls as young as 12 in Liberia are regularly having sex with men - often humanitarian workers and peace-keeping soldiers - in return for money or food, a British charity revealed today.
The girls "sell sex" or get involved in "man business" to gain essential goods to help their impoverished families survive.
Often the men they are having sex with are the very people to which such exploitation should be reported, it was claimed.
The report, entitled From Camp to Community: Liberia Study on Exploitation of Children, was carried out by Save the Children.
A total of 315 people were interviewed, 23% were boys and 26% were girls while 27% were men and 24% were women.
Half were refugees living in camps within their own troubled country (internally displaced people or IDPs) while the other half had returned to their homes after years of conflict to live in makeshift communities.
The study found that girls aged from eight to 18 were involved in sexual activities with men but that girls of 12 and upwards were providing sex regularly.
"They are between 10 and 15 years; as soon as they see their 'tete' (breasts) coming up then they jump in this man business," one interviewee said.
Reasons for having sex with the men - aged on average between 30 and 60 - varied from economic deprivation, pressure from peers and parents, seeing other children with material goods and boredom.
Many more young women were found to be having sex with adult men in the hope of payment than mature women.
The report said: "The over-riding reason cited for this is that men can have sex with young girls for very little in return, sometimes nothing."
Save the Children found numerous groups of men were guilty of exploiting young girls including businessmen, police officers, teachers and peace-keeping soldiers.
Humanitarian workers and those running the camps were also guilty.
"All focus groups and individual interviewees without exception mentioned NGO workers," the study claimed.
"In all the IDP camps where discussion groups were conducted, the Camp Management Committee (CMC) and block leaders were implicated."
Another interviewee told Save the Children: "In the camp, most camp officials were loving to (seeking sex with) children.
"During distribution (of food and goods), when these people have interest in some of the girls, the authorities serve them very fast.
"After the distribution they would arrange an appointment with these girls."
Sex takes place in distribution centres, entertainment area, bushland and even latrines and washing areas.
The study found that many parents knew that sex was going on but "accept it because of poverty and the dire situation in the camps".
Among the underage girls having sex, most were afraid to report it because by implicating NGO staff, for example, could lead to NGO support being withdrawn.
"They would not know where to report it as the Camp Management Committee and block leaders were themselves involved in it," the report said.
Save the Children's UK chief executive Jasmine Whitbread called on the Liberian government, the UN and international NGOs to do more to fight the problem.
"This cannot continue," she said. "It must be tackled.
"Men who use positions of power to take advantage of vulnerable children must be reported and those who are taking advantage of their position must be fired.
"More must be done to support children and their families to make a living without turning to this kind of desperation."