Penny Lawrence, the deputy chief executive officer of international charity Oxfam, resigned on Monday saying she took “full responsibility” for failing to respond adequately over allegations of sexual misconduct by the organisation’s aid workers in Haiti and Chad, Reuters reported.

Former aid workers of Oxfam, one of Britain’s biggest charities, in Haiti have been accused of paying for sex while on a mission to help those affected by the 2010 earthquake. While the accusations go back to 2011, it has been in the news after the Times published a report about it on Friday.

“Over the last few days we have become aware that concerns were raised about the behaviour of staff in Chad as well as Haiti that we failed to adequately act upon,” Lawrence said in a statement. “It is now clear that these allegations, involving the use of prostitutes and which related to behaviour of both the country director and members of his team in Chad, were raised before he moved to Haiti.”

“As program director at the time, I am ashamed that this happened on my watch and I take full responsibility,” she said. “I am desperately sorry for the harm and distress that this has caused to Oxfam’s supporters, the wider development sector and most of all, the vulnerable people who trusted us.”

The Times report said that Oxfam’s country director for Haiti, Roland van Hauwermeiren, allegedly had prostitutes over at a villa Oxfam rented for him. The report said Oxfam knew about the allegations and even launched an internal investigation that led to four aid workers being dismissed and three others, including van Hauwermeiren, resigning.

In its report about the allegations, Oxfam said “serious misconduct” had taken place in Haiti, without going into the details. After the report came out on Friday, Oxfam denied trying to cover up any of these allegations. Soon after, other reports emerged that said former employees in Chad alleged that prostitutes were repeatedly invited to the Oxfam team house, and a senior member had been fired for his behaviour in 2006. van Hauwermeiren was head of Oxfam in Chad at the time.