Girls as young as eight are being forced to have sex in exchange for food by workers for local and international agencies, according to its report.
The UN in Liberia said it would investigate specific allegations.
The United Nations promised to put safeguards in place after sexual abuse in the refugee camps of West Africa was first revealed four years ago.
But a study by Save the Children, which involved speaking to more than 300 people in camps for people displaced by the war, found that abuse was still widespread.
Girls from the age of eight to 18 years were being sold for sex, “commonly referred to as ‘man business’,” the report noted.
Source: BBC News