Oxfam faced fresh pressure after a former senior member of staff said her concerns about "a culture of sexual abuse" involving aid workers had been ignored.
Helen Evans, who was in charge of investigating allegations against Oxfam staff members between 2012 and 2015, told Channel 4 television that abuse cases she had heard of included a woman who had been coerced to have sex in exchange for aid.
Another involved an assault on a teenage volunteer by a staff member in a charity shop in Britain, she said.
A survey of Oxfam staff in three countries including South Sudan showed around 10 percent of staff had been sexually assaulted and others had witnessed or experienced rape or attempted rape by colleagues, Evans said.
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.
"I felt that our failure to adequately resource was putting people at risk," she said in an interview broadcast by Channel 4 late on Monday. "I struggle to understand why they didn't respond immediately to that call for additional resource."
One of the best-known international NGOs, with aid programmes running across the globe, Oxfam is under threat of losing its British government funding over the sexual misconduct allegations.
Asked about Evans's allegations, Oxfam said her work had spurred the organisation into taking concrete steps to improve the way it deals with "safeguarding" issues.
"We regret that we did not act on Helen's concerns much quicker and with more resources," the statement said.
"We have doubled the number of people to four in our dedicated safeguarding team and we are in the process of recruiting two extra staff."...