Former international development secretary Priti Patel has demanded that Oxfam chief executive Mark Goldring resign over the sex scandal which has engulfed the charity.
Oxfam's deputy chief Penny Lawrence has already quit, following a report in the Times which alleged that the charity covered up an internal inquiry into the use of prostitutes by staff in Haiti seven years ago.
But Patel, who resigned her ministerial brief in November over unofficial meetings with Israelis, shortly after raising the issue of exploitation in a speech to the United Nations, said Goldring must also stand aside over his charity's failures of accountability and safeguarding.
"I don't think they can draw a line in the sand [with Lawrence's resignation]," Patel told Julia Hartley-Brewer.
"Any organisation, whether it's a charity, a business, you name it... the head, the leader of the organisation, they are accountable.
"I think it's untenable for him to stay. The failures have happened on his watch."
Even after the scandal broke, Patel said, she was appalled to read a press release from Oxfam describing the behaviour of staff in Haiti as "misconduct." The behaviour clearly amounted to a crime, she said, and should have been treated as such.
"They [Oxfam] are operating not as a humanitarian charity... the abuse and crimes committed by aid workers are absolutely repulsive."
As part of her discussions with the UN last year Patel proposed a series of recommendations, notably the creation of a new protocol to facilitate investigations by UK authorities whenever a child abuse accusation is made against a British national.
She told Julia that the UN had "ignored the shocking scandal of abuse" for years and fundamental issue was now needed across the sector.
However the Tory MP rejected suggestions that her attack on Oxfam was driven by a political agenda, specifically the Conservative desire to cut Britain's aid budget.
"That's appalling," Patel said. "Child abuse is not a left or right issue.
"This isn't a race to the bottom. If people choose to withhold their funds, that's a personal choice and a matter for them. We live in a free society.
"The important thing is we have transparency, accountability and justice."