Oxfam said that four members of staff implicated in misconduct were fired, and a further three including the country director at the time left voluntarily during an internal investigation in 2011.
Oxfam said Friday it will set up an independent commission to take a look at the organization's practices, with a mandate to investigate past and present sexual exploitation claims.
Allegations grew after senior aide workers were accused of paying for prostitutes and downloading pornography while helping the Haiti 2010 effort.
"We will continue to support Oxfam's incredible work for many more years to come", she added.
Similar accusations emerged after van Hauwermeiren and his team were reassigned to Haiti following the devastating 2010 quake there.More news: Rain/ snow mix early Saturday, warming weekend
She said their sexual relationship began shortly afterwards and remembers she was "17 because it was right after I had the child".
She said the organisation was "hurt", but added: "There is no way this organisation can die. the world needs it".
A former Haitian prostitute has come forward saying that Roland van Hauwermeiren, the former Oxfam director, used to pay her for sex twice a week after the 2010 quake destroyed her home and killed five members of her family.
Oxfam has confirmed that it dismissed van Hauwemeiren a year ago over the allegations; however, he said in the Dutch-language letter that he left of his own accord after failing to control rumors of sex scandals.
"It was, in my opinion, a mature honourable lady, not an quake victim and no prostitute, whom I met since I supported her young sister and very young mother with diapers and powdered milk".
Ms Gabo said they exchanged "good evenings" and Mr Van Hauwermeiren asked where she lived, then told her: "I find you very sexy, how can I help you?"More news: Saturday snow: what to expect
"The intensity and the ferocity of the attack makes you wonder, what did we do?"
"He would bring back children's clothing for the toddler and he brought things for me", she said.
International Development Secretary Penny Mordaunt has threatened to cut the charity's government funding, which was £32m previous year.
In response, Oxfam said it would create a global database of accredited referees to crack down on forged or unreliable references from past or current employees.
Oxfam GB's chief executive Mark Goldring, who has resisted pressure to resign, said the charity had "betrayed people's trust" and would work with the Government, the Charity Commission and others to reform.More news: Japan's Hanyu wins gold in men's figure skating
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