Penny Lawrence today resigned as deputy chief executive of Oxfam, following several days of negative coverage as the charity was widely criticised over its handling of sexual misconduct in 2011.
On Sunday the charity announced a raft of new measures to improve its safeguarding.
The charity's senior leaders met with the international development secretary and the Charity Commission earlier today, after the Times revealed details of senior staff paying for sex in Haiti. Oxfam has been criticised for not being open enough with the Commission, DfID or the public.
'I take full responsibility'
Lawrence said: "I am deeply sad to announce that I have resigned as deputy chief executive of Oxfam GB.
"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.
"As programme director at the time, I am ashamed that this happened on my watch and I take full responsibility.
"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.
"It has been such a privilege to work for such an amazing organisation that has done and needs to continue to do such good in the world."
Mark Goldring, chief executive of Oxfam GB, 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."
DfID: Oxfam ‘must deliver progress’
Mordaunt met with Mark Goldring, the chief executive of Oxfam, and Caroline Thomson, its chair, yesterday and told them they must make improvements and report back by the end of this week.
Neither Goldring, nor Thomson were at the charity in 2011.
“Oxfam made a full and unqualified apology – to me, and to the people of Britain and Haiti - for the appalling behaviour of some of their staff in Haiti in 2011, and for the wider failings of their organisation’s response to it,” Penny Mordaunt, international development secretary said.
She added that she had been assured that the charity is “cooperating fully with the authorities in Haiti and will do so in any other country where abuse has been exposed”.
The perpetrators in Haiti were not British nationals and Mordaunt has now directed Oxfam to “immediately provide full details of those involved to the governments of their home countries, so that appropriate legal processes can be taken forward”.
Oxfam must also “confirm to DfID by the end of the week precisely how they will handle any forthcoming allegations around safeguarding - historic or live - in a way in which the public can have confidence. We expect this process to include an independent and external element of scrutiny”.
Mordaunt said Oxfam must “demonstrate the moral leadership necessary to address this scandal, rebuild the trust of the British public, their staff and the people they aim to help, and deliver progress on these assurances” and that she would judge the charity on “actions going forward”.
Responding to Mordaunt, Thomson said the charity was committed to improving.
She said: "I would like to thank the secretary of state for a very challenging but constructive conversation. We unreservedly apologised to her as well as to our supporters, donors and the people of Haiti for the things that happened in our name.
"We told her of the significant improvements since 2011, including setting up a dedicated safeguarding team but also set out our plans for significant changes in our operations to ensure such events are less likely to occur and if they do are handled differently in future. In particular we assured her of our commitment to full accountability and transparency in all our operations and said that a special Trustee group, chaired by me, would monitor implementation.
"Oxfam is in total agreement with the secretary of state's further proposals. We recognise that we have some way to go to persuade her that we have the right moral leadership to be fully entrusted with public money. But we are committed to working with her, DFID and the Charity Commission to prove we can meet her expectations."