By David Loyn
BBC Developing World correspondent
People displaced by the war are among the most vulnerable
Sexual exploitation of girls in Liberia is still widespread according to research by Save the Children.
Soldiers from the UN peacekeeping force, aid workers, and teachers are among those who demand sex from girls some as young as eight.
"We're talking about some of the most vulnerable children being abused and exploited by those people who have money and power," Tirana Hassan from Save the Children said.
All of the groups spoken to in the research mentioned aid workers as being involved, trading the distribution of food and other supplies in return for sex.
After this was first exposed in camps for internally displaced people four years ago, even before the war ended, the international community put in safeguards that should have stopped it happening again.
But the research found that, "sex in exchange for goods, services and as a means of survival was becoming a more common option for children to support themselves and their families".
According to this report, the exploitation of young children also involves government employees and businessmen, while teachers demand sex in lieu of school fees, or even just to give good grades.
More than a million people were displaced in the war, and Liberia remains one of the poorest countries in Africa, with typical monthly salaries of around $50. In this climate of chronic poverty, sexual exploitation has become routine.
Konah Brown, aged 20, who has a four-year-old daughter, remembers that in order to get a bar of Oxfam soap, she had to sleep with the man who was distributing it.
Most recently she says she was forced to have sex with a worker for the World Food Programme.
"This young man had been doing it to most of my friends. And the children too don't have strong minds. They will have sex with him to get the food," she said.
Konah lives in one of the 25 camps, mostly dotted around the capital Monrovia, that are now being dismantled as people return home.
But as opportunities for exploitation here reduce, the unequal trade in sex for small favours is spreading back to villages across the country.
In one returnee community, Awa Kanakhai said that she too was forced to sleep with a WFP worker to receive food, and she said that those involved were not only local Liberian employees.
"Some are Liberian and some are foreign".
The most visible signs of abuse are close to garrisons of UN peacekeeping soldiers.
In one village a 17-year-old girl said that most of her teenage friends were having sex with Ghanaian soldiers from the nearby base. Like many of them she has a baby fathered by a Ghanaian soldier.
The UN's Humanitarian Co-ordinator in Liberia, Jordan Ryan, said that specific allegations would be investigated.
"Unfortunately not all international NGOs have taken it seriously. But it is a clear priority. We have never done enough until there's a zero case load. Has enough been done? Not yet. Are we working on it? You bet we are."
Save the Children held a series of workshops in Monrovia last week to highlight the issue among other international organisations.
They say, "it is clear that the steps taken to date are not addressing the problem sufficiently".