Children interviewed by the UNHCR and Save the Children in refugee camps in Liberia, Guinea and Sierra Leone for the report accuse not just aid workers of sexual abuse, but claim they have also been exploited by UN peacekeepers and community leaders.

The internal report - commissioned by the agencies in response to concern over numerous reports of child abuse by aid workers - says that in all three countries the workers used "the very humanitarian aid and services intended to benefit the refugee population as a tool of exploitation".

In testimonies taken mainly from girls under 18, more than 40 agencies and non-governmental organisations were named along with nearly 70 individuals. Save the Children has sacked one of its employees and two of its volunteers and has promised to put a stop to the practices. Some UNHCR workers have also been accused of sexual exploitation.

Many of the girls said they believed that in order to get rations they had to provide sexual favours: they did not know it was their right. Many also spoke of negotiating sex for shelter, education and medicine. Some girls talked of getting better grades if they had sex with their teachers.

The report says the problem is worst in places where there are well established aid programmes and is particularly pronounced in refugee camps in Guinea and Liberia.

Last night, UNHCR and Save the Children UK said it had made details of the report available because of the disturbing nature of the allegations, the apparent scope of the problem, and the need for immediate and coordinated remedial measures by a wide range of agencies.

The report states: "Most of the alleged 'exploiters' were male national staff who traded humanitarian commodities and services for sex with girls under 18". The two agencies said, however, that the assessment team could not verify the allegations.

Measures will now be introduced by Save the Children and UNHCR to combat child abuse in the region. Security will be increased and more female staff will be employed in the camps.

Refugee girls who are most vulnerable to sexual exploitation will be identified. Aid will be provided to all refugees so that it meets their minimum needs and refugee children will be informed of their rights and entitlements.