She also wanted charities to ensure any historical concerns have been properly handled, and spell out their policies for handling such cases.
Responding to claims that some of the charity's workers hired prostitutes during a mission to the Caribbean country in 2011, Lord Leslie Griffiths said he repeatedly came across similar accusations during his 40 years' experience in humanitarian work. Maybe the scandal will even trigger a long-overdue debate about the limits of foreign aid.
Still, it's unclear whether the resignation and the apology will quell the scandal, which first emerged when the Times of London reported last week that seven former Oxfam staff members who worked in Haiti faced misconduct allegations that included using prostitutes and downloading pornography.
Meanwhile, Tory MP and former worldwide development secretary Justine Greening has told Sky News that she is "absolutely shocked" to hear of the claims that some of the charity's employees used prostitutes in the country.
Allegations emerged on Friday claiming Oxfam's country director for Haiti, Roland van Hauwermeiren, used prostitutes at a villa rented for him by Oxfam in the aftermath of the 2010 quake.
Oxfam has said that as a result of its internal investigation in 2011, four people were dismissed, and three others - including the Haiti country director who had previously held the same role in Chad - had resigned.
Mordaunt had threatened to pull public funding from Oxfam unless the charity revealed everything it knows about the Haiti allegations.
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"It's not a reason to cut the budget, it's a reason to manage it carefully".
"Our approach to this matter would have been different had the full details that have been reported been disclosed to us at the time".
The chief executive said: "With hindsight, I would much prefer that we had talked about sexual misconduct. I'm not the kind of person who would have ignored anything like that - why would anyone?"
It said it will ensure that the inquiry's findings are put on the public record. In December 2017 the regulator told Oxfam it needed to improve its overall governance and safeguarding in a case report.
Oxfam executives met with the International Development Secretary Penny Mordaunt yesterday in an attempt to assure the minister that the charity could be trusted with the £32m (€36m) of public funding it receives.
She also wrote to all United Kingdom charities working overseas to insist they give her specific assurances that they have reported everything untoward to the relevant authorities.
On February 11, the United Kingdom minister for global development Penny Mordaunt accused Oxfam of doing "absolutely the wrong thing" by failing to disclose details of the internal investigation. It also reminded charities to review their safeguarding practices and procedures if they had not done so in the last 12 months.
Abby Maxman, president of Oxfam America, Monday in a statement that she was "appalled and dismayed" by the revelations but determined to learn from them.