An international watchdog should be set up to urgently investigate child sex abuse by aid workers and peacekeepers, the British charity Save the Children said Tuesday.
The group said action was needed after its researchers unearthed what they called "widespread" evidence that children as young as six were being traded for food, money, soap and even mobile phones in war zones and disaster areas.
Save the Children's findings was based on work with hundreds of youngsters from Ivory Coast, southern Sudan and Haiti, said the charity's chief executive Jasmine Whitbread.
"This research exposes the despicable actions of a small number of perpetrators who are sexually abusing some of the most vulnerable children in the world, the very children they are meant to protect," she added.
"It is hard to imagine a more grotesque abuse of authority or flagrant violation of children's rights."
The charity said "endemic failures" in responding to the abuse that was officially reported were letting down the abused, and better reporting mechanisms should be introduced.
Whitbread said the United Nations, the wider world as well as humanitarian and aid agencies have made important commitments to tackle the problem in recent years.
But most had failed to turn their promises into action, she added, calling for all agencies working in emergencies, including her own, to "own up to the fact that they are vulnerable to this problem and tackle it head on".
The reputation of UN peacekeepers has been tarnished in the past by cases of sexual abuse against women, notably in Democratic Republic of Congo, Ivory Coast and Haiti.
In November last year, the UN said that more than 100 Sri Lankan soldiers were to be sent home over charges that they paid for sex while stationed in Haiti.
After turning a blind eye for decades to cases of abuse by its peacekeepers the world body recommended in 2005 that erring soldiers be punished, their salaries frozen and a fund set up to help any women or girls made pregnant.
The "zero tolerance" policy towards sexual misconduct includes a "non-fraternisation" rule barring them from sex with locals.
It was brought in after revelations in December 2004 that peacekeepers in DRC were involved in the sexual abuse of 13-year-old girls in exchange for eggs, milk or cash sums as low as one dollar.