"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".
A decision on whether to withdraw public funding from Oxfam over the aid worker sex scandal will not be taken hastily, International Development Secretary Penny Mordaunt has said.
The charity's deputy chief executive, Penny Lawrence, who joined Oxfam in 2006 as worldwide programmes director resigned yesterday.
"I also wrote a thorough and detailed letter to each and every Oxfam staff member worldwide reiterating the behaviours we expect of them and the code of conduct". There was no immediate comment from Oxfam.
Announcing the Charity Commission's decision to open an inquiry into Oxfam, the regulator's deputy chief executive, David Holsworth, said: "Charities and dedicated, hard-working aid workers undertake vital, lifesaving work in some of the most hard circumstances across the world".
The Labour frontbencher said: "The Charity Commission and Government departments have serious questions to answer: why did they take no action in response to concerns raised by Helen Evans in June 2015 and August 2015?"
Ms Evans, who was at the charity for more than six years, also said overseas staff had traded aid for sex with ten per cent of workers either witnessing abuse or being sexually assaulted.
The Oxfam sex scandal has intensified with further allegations of misconduct by charity workers emerging.
Reuters could not independently verify the allegation.
Oxfam is battling the fallout from revelations some of its staff engaged sex workers while delivering aid after the 2010 quake in Haiti.
"As program director at the time, I am ashamed that this happened on my watch and I take full responsibility".
Country director Roland van Hauwermeiren, 68, admitted to having sex with vulnerable prostitutes at his Oxfam-funded villa in Haiti until his resignation in 2011.
Reuters was unable to reach any of the Oxfam staff who worked in Haiti at the time.
A pedestrian walks past a branch of Oxfam, in London.
Oxfam has been warned that it could lose over 32 million euros of European funding over the scandal. Whether or not it loses that funding, private donations could be hit by the bad publicity.
The allegations surrounding Britain's best-known charity Oxfam only seem to deepen with each passing day. Its 650 shops selling second hand clothes and books to raise funds are a familiar sight on the high street.
The former Richmond MP also knows that the continuing lurid claims about the sexual exploitation of the most vulnerable, the victims that the charities were supposedly helping, will make it harder to justify the £13bn a year that Britain now spends in this field when domestic policy priorities are denied funds.
Meeting the United Nations target was a policy championed by former Conservative Prime Minister David Cameron as part of his efforts to re-brand his party as more compassionate.
"[There was] another case where a woman had been coerced to have sex in exchange for aid and another one where it had come to our attention that a member of staff had been struck off for sexual abuse and hadn't disclosed that, and we were then concerned about what he might be doing", she said.
"It's not a reason to cut the budget, it's a reason to manage it carefully".