An estimated 73 per cent of Guinean children work, 61 per cent of them as domestics.
Although the report is based on field work in Guinea, it provides a snapshot of a problem that is widespread in Africa.
Human Rights Watch said recruitment of child workers is considered normal in West Africa and happens in a wider context of migration, gender discrimination, and poverty.
|"He has threatened me with a knife and said I must not tell anyone. He does it each time his wife travels. I am scared" |
15-year-old domestic worker
Children from poor, rural families are often sent to live with wealthier, urban relatives as part of a custom of "confiage" or child fostering.
Parents see it as a way of making sure their daughters are at least fed while others hope that the girls will receive an education, Juliane Kippenberg, a researcher in the children's rights division of Human Rights Watch, said.
While there are examples of children that have had a positive experience and received an education, the system is largely one of exploitation and is riddled with abuse.
The report quoted a 15-year-old girl, who was sent to work as a domestic helper for a woman in the capital, Conakry.
The girl, who was not named for her safety, said: "When she [his wife] is gone, her husband wakes me up and rapes me.
"He has threatened me with a knife and said I must not tell anyone. He does it each time his wife travels. I am scared."
A 14-year-old girl told Human Rights Watch that she had been sent to care for her aunt's children.
The girl said: "She promised that afterwards I would go to school or do an apprenticeship.
"But since I am there, the child has grown up, goes to school now, but not me. Up to now, it is me who does everything in the house."
Although most of the girls are sent to live with relatives, many end up cooking, cleaning, and caring for the children of strangers.
Child trafficking is a problem across West Africa, with children also forced to work in mines or on the streets around the region, others are taken to Europe for use in the sex trade.