Aid workers traded wheat and life-saving medicines for sex with children in crisis zones, it has emerged.

Humanitarians traded 'oil, bulgur wheat, tarpaulin or plastic sheeting, medicines, transport, ration cards, loans, education courses and skills training' with girls aged 13 to 18.

The report, written in 2001, shows officials knew of the alleged abuse in Africa a decade before the Oxfam sex scandal, where chiefs were accused of concealing findings of an inquiry into claims staff paid for prostitutes in disaster-struck Haiti in 2011.

Underage girls were also asked to pose naked for pictures and rooms were rented for sex, the report by Save the Children and the United Nations High Commissioner For Refugees (UNHCR) reveals.

Haitians reach towards aid being dispense from the back of a food distribution truck in 2010

It added in some cases that parents encouraged their daughters to be sexually exploited by aid workers, government officials, UN peacekeepers, refugee leaders and teachers to bring income into the family.

It comes as a British-funded charity supported by Meghan Markle admitted its workers traded food and cash for sex with survivors of the devastating 2010 earthquake on Haiti.

World Vision, which Prince Harry’s fiancée was an ambassador for until last year, admitted that paid employees forced desperate survivors of the disaster to have sex or money for World Food Programme aid.

The UNHCR and Save the Children probe shows abuse was rife in Guinea, Liberia and Sierra Leone.

While security forces pooled cash to have sex with children, aid workers withheld provisions for children unless sex was given.

One refugee in Guinea told investigators aid workers would ask for sex in exchange for a kilo of lifesaving soya nutrients.

A teenage girl in Liberia said: 'It's difficult to escape the trap of those people. They use food as bait to get you to have sex with them.'

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More than 40 aid agencies working in West Africa were named in the report along with 67 individuals.

It says the majority of children consulted said they knew of at least one other child involved in an exchange that involved trading sex for life-saving commodities.

In some cases, children as young as four were sexually harassed.

It states: 'Girls between the ages of four and 12 were also reported as being sexually harassed, either verbally or through touching of buttocks, breasts, or genitals. Children said boys of their age group also did the same, but that adult males were mostly responsible.

Displaced Haitians walk the streets amidst collapsed buildings and rubble in downtown Port Au Prince, Haiti in January 2010

'Children reportedly experience attempted rape mostly when they go to use the toilets or take a bath. The toilets and bathrooms are all located in the same place, and divided along gender lines. Children say adult males lay watch for when the child is going to the toilet. They then follow the child and try to rape them.'

The report also explains that the children are aware of the exploitation, but often feel they have no other options.

'The children themselves, whilst aware of the exploitative nature of the exchange, felt this was often the only option they had in order to receive food and other basic necessities and to pay for education.

'Parents were often aware of the exploitation but also felt that there were no other options for their family to secure a livelihood and whilst not approving it, generally turned a blind eye.

In some cases, however, it was reported that parents encouraged their daughters to engage in such activities to bring an income into the family' it says.

Oxfam in numbers: How much money does the scandal-hit charity make each year and how is it spent? The charity's annual review provides a breakdown of income and spending for Oxfam GB each year. Here are the headline figures from the 2016/17 report. £408.6 million Oxfam's total income in 2016/17. The Government and public authorities provided 43% of the total, at £176 million, while donations and legacies made up the second largest proportion of the charity's income at £108 million. £303.5 million The amount Oxfam spent on charitable activities in 2016/17. 41% The percentage of Oxfam's funds that went on humanitarian spending in the last financial year, which the charity describes as saving and rebuilding lives after disasters. Development, described as helping 'communities and families lift themselves out of poverty', made up 38% of spending. 21% The remaining 21% was spent on support costs (10%), fundraising (8%) and campaigning and advocacy (3%). 31 The number of worldwide emergencies the charity responded to in 2016/17. 8.6 million The number of people hit by conflict and natural disaster for whom the charity provided emergency support during the last financial year. 5,083 The number of staff employed by Oxfam as of March 31 last year. £130,000 to £139,000 One member of staff earned between £130,000 and £139,000 in the year to March 31 2017, the highest bracket available. The figure could be made up of a number of things including salary, taxable benefits and other allowances; for example, the charity pays towards the cost of education for up to three children where suitable free schooling is not available. Advertisement

The investigation also found that sometimes younger girls were befriended so aid workers could gain access to their mothers or older sisters, and some teenage boys were also exploited by older women.

It also alleges agency workers could ask girls for sex in 'exchange for employment and continued to demand sexual favours even after the girls were employed'.

A female agency worker in Guinea said 'No girl will get a job without having sex with NGO workers. The girls see it as competition. It is survival of the fittest'

The study of more than 1,500 people revealed that senior staff often allowed agency workers to 'behave with impunity' and that aid workers were 'most frequent sex exploiters of children, often using the very humanitarian aid and services intended to benefit the refugee population as a tool of exploitation'.

The newly resurfaced report comes in the wake of the Oxfam sex scandal, where it has emerged prominent figures in the charity slept with prostitutes while on humanitarian missions

The report adds: 'Peacekeepers are alleged to have sexually exploited children in exchange for money and food.

'It is claimed some very young children have been asked to pose naked in exchange for biscuits, cake powder and other food items.

'Some are alleged to have had sex with the girls without using condoms. Peacekeepers reportedly pay from US $5 to $300 for sex with children.'

The newly resurfaced report comes in the wake of the Oxfam sex scandal, where it has emerged prominent figures in the charity slept with prostitutes while on humanitarian missions.

Oxfam chief Roland van Hauwermeiren, 68, admitted to giving a woman baby milk and nappies in Haiti in 2010 after sleeping with her.

The Belgian, who has now left his post, had sex with a Haitian woman in a villa rented by the charity.