The European Commission is demanding EU-funded charities to explain measures they are taking to prevent abuse.

Over 200 aid organisations and NGOs signed an agreement with the EU commission as a precondition for funding. On Thursday (15 February), the Brussels-based executive sent a letter to each, asking them for details.

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The signed agreements include measures to "ensure 'zero tolerance' for sexual exploitation and abuse." The commission letter comes amid a scandal of alleged sexual abuse by some staff at the UK charity group Oxfam.

The issue has gripped headlines with threats of funding cuts, following a newspaper report in The Times last week that some Oxfam staff paid for sex with prostitutes during a 2011 post-earthquake relief mission in Haiti.

Oxfam then later rehired one of the workers who had been fired for sexual misconduct in Haiti.

Earlier this week, the EU commission announced that it wanted Oxfam to clarify the allegations. Oxfam UK had received some €1.7m in EU funds for the Haiti effort.

On Friday, the British charity announced the launch of an independent commission led by women's rights leaders to probe Oxfam's handling of sexual misconduct cases.

It also announced it would publish a 2011 internal investigation into staff involved in sexual and other misconduct in Haiti "as soon as possible, after taking steps necessary to protect the identity of innocent witnesses."

Winnie Byanyima, executive director of Oxfam International, said in a statement that they would also triple the amount of funding, to €1 million per year, to help safeguard vulnerable people, set up a global database of accredited referees to ensure sex offenders are never hired, and initiate a culture change to weed out all forms of abuse.

"What happened in Haiti and afterwards is a stain on Oxfam that will shame us for years, and rightly so," she said.

Some of its biggest supports, such as archbishop Desmond Tutu, have since resigned as Oxfam ambassadors. Oxfam is one of the world's largest disaster relief charities and employs around 10,000 people.

A similar but separate issue surfaced last year after Mercy Corps, another EU-funded NGO, publicly announced that it was investigating allegations of sexual misconduct by two of its staff on the Greek island of Lesbos.

In May, one of its beneficiaries had filed a complaint over its hotline. But a ten-week investigation into the single complaint did not substantiate the allegations, Mercy Corps said in an email.

"The EU did not withdraw our funding and we are thankful that they did not do so based on a single allegation we reported to them immediately," said a Mercy Corps spokesperson.

The NGO is, however, undergoing a probe by the EU's anti-fraud office, Olaf.

Olaf confirmed to EUobserver that it had opened "an investigation into allegations of fraud and irregularities in relation to a project aimed at providing cash assistance to refugees hosted in Greece". But it declined to comment on whether the probe was aimed at Mercy Corps.

The probe is looking into an EU-funded project aimed at providing cash assistance to refugees hosted in Greece. The grant money for the project has since been suspended.