The Good Will Hunting star said she was "nothing short of horrified" by the allegations against the charity.
After meeting Oxfam officials on Monday, Mordaunt said she had written to all British charities working overseas to demand that "they step up and do more, so that we have absolute assurance that the moral leadership, the systems, the culture and the transparency that are needed".
Evans, who headed a "safeguarding" section responsible for protecting staff and the people Oxfam works with, spoke of frustration that her calls for more support for her team were not taken seriously enough. Oxfam International is in deep trouble after being hit with the scandal - the organisation has already lost 1,270 members over the weekend (10-11Feb18), with former subscribers calling in to cancel their monthly donations in response to the sex scandal.
Documents provided by Oxfam have led to further questions and suggest that the charity might not have "fully and frankly disclosed material details about the allegations at the time", the Charity Commission said.
The Charity Commission said it had contacted Save The Children to establish if it had records of Ms Miller's complaints.
The cancellations are double the average cancellation rate of 600 per month, BBC reported.
Talking about how charities receiving United Kingdom aid have been told to show "full transparency", Penny Mordaunt said: "If our standards are not met, then the British taxpayer will not continue to fund them". "The case for the type of work done by Oxfam is too strong to allow it to be undermined by bad behaviour", he said.
Scotland's global development minister, Alasdair Allan, has held crisis talks with Oxfam seeking assurances that projects involving the Scottish Government are not caught up in the charity's prostitution scandal.
The actress has become the first high profile celebrity to publicly withdraw her support for the charity over the Haiti controversy.
The DofE Award said in light of the allegations, it would "be reviewing our association with Oxfam as a participant volunteering provider".
An Oxfam store in London.
In another blow to the Oxfam brand, prosecutors in Guatemala said that they had detained Juan Alberto Fuentes Knight, the chairman of Oxfam International.
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