Oxfam's deputy chief executive has quit in the wake of the aid worker sex scandal saying she was "ashamed" of what had happened.
Penny Lawrence said she took full responsibility for what had happened on her watch and was sorry for the "harm and distress" it had caused supporters.
Oxfam has faced intense criticism over its handling of sex allegations, including the use of prostitutes by workers in Haiti in 2011.
Ms Lawrence (pictured) said: "As programme director at the time, I am ashamed that this happened on my watch and I take full responsibility."
The resignation comes after claims on Monday that the charity was aware of concerns about the conduct of two of the men at the centre of the allegations in Haiti when they worked previously in Chad.
Ms Lawrence said: "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. 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."
She added: "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."
Oxfam chiefs were called in for crisis talks with International Development Secretary Penny Mordaunt following the claims of sexual misconduct by its staff.
Ms Mordaunt said on Sunday the charity had lied and failed in its "moral leadership" by failing to fully disclose details of its investigation into the misconduct to relevant authorities.
The charity received £31.7 million in Government funding in 2016/17 but the support has been put at risk by the scandal.
Charity Commission director of investigations Michelle Russell said the watchdog was not told the full story at the time Oxfam first investigated allegations of misconduct in 2011.
She told BBC Radio 4's Today programme: "We've made very clear that had the details of what has come out over the last few days been told to us, we would have dealt with this very differently.
"We were categorically told there was no abuse of beneficiaries involved in the allegations. Nor were we told that there were issues or possible issues around possible crimes, including those involving minors."
Four members of Oxfam staff were dismissed and three, including the country director, Roland van Hauwermeiren, resigned before the end of the 2011 investigation.
According to The Times, Oxfam knew about concerns over the conduct of Mr van Hauwermeiren and another man when they worked in Chad before they were given senior roles in Haiti.
Mr Van Hauwermeiren's attitudes and behaviour towards women were documented, it said.
He also reportedly allowed the other man, a Kenyan, to stay in his job despite handling at least four complaints of sexual harassment or misconduct against him.
Oxfam chief executive Mark Goldring said: "I deeply respect Penny's decision to accept personal responsibility. Like us, she is appalled at what happened and is determined to do what is best for Oxfam and the people we exist to help.
"I would like to place on record my sincere thanks for the years of dedicated service that Penny has given to Oxfam and the fight against poverty around the world."
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) Charlotte Ball / Oxfam / PA Wire.