According to The Observer, women were repeatedly invited "for parties" at Oxfam's team premises.
"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 commission said.
Mordaunt said she was taking action to make sure charities were "properly regulated" after the allegations.
If the moral leadership at the top of the organisation is not there then we can not have you as a partner.
In an emailed statement to dpa on Sunday, Oxfam said it would "strive to clarify as soon as possible whether the [Chad] allegations were known to us and what measures were taken".
Britain's worldwide development secretary Penny Mordaunt told the aid agency to front up tomorrow in London to explain why it appeared to cover up a sex scandal.
"I had quotes from the United Nations report", she said.
Internet rights advocate John Perry Barlow dies
In a 2004 interview with Reason, Barlow was prescient about how the internet would evolve as a business platform. Barlow also collaborated with singer/guitarist Bob Weir , but also co-wrote with keyboardist Brett Mydland .
"With hindsight, I would much prefer that we had talked about (the) sexual misconduct", Goldring told BBC radio.
"Moreover we received positive references from former Oxfam staff-in their individual capacities-who worked with him", including from a human resources staffer, a spokesman said.
The government's hardening stance follows reports in The Times newspaper that young sex workers were hired by Oxfam's senior staff in Haiti after the 2010 quake which devastated the island and left up to 300,000 people dead.
The former Secretary of State said that "the reason why Oxfam has landed in this position is because they have not been fully open and transparent about what happened".
Responding to a report in The Times newspaper, Oxfam admitted that the behaviour of some of its staff had been "totally unacceptable".
An Oxfam report on the investigation stated there had been no allegations of abuse of beneficiaries and made no mention of any potential sexual crimes involving minors.
The British Red Cross said a "small number of cases of harassment" had been reported in the UK.
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Although the charity has denied covering up the alleged scandal, Christian Aid said the claims are "deplorable".
But as well as being a public relations disaster for Oxfam, the scandal could cost them $50 million in government funding.
Oxfam chief executive Mark Goldring apologised on Saturday, saying he was deeply ashamed of Oxfam's behaviour.
He added: 'Everybody - the 25,000 staff and volunteers - are compromised by this, the hundreds of thousands of people who support Oxfam every month are compromised by this, and to everybody I apologise.
Oxfam's chairwoman of United Kingdom trustees, Caroline Thomson, said it was working to "address the underlying cultural issues that allowed this behaviour to happen".
"It doesn't matter whether you've got a whistleblowing hotline, it doesn't matter if you've got good safeguarding practices in place".
She added that Oxfam had done "absolutely the wrong thing" by failing to inform authorities about the full details of the allegations.
Eurostar to launch London-Amsterdam direct service in April
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