Oxfam has received 26 allegations of misconduct since the Haiti sex scandal erupted two weeks ago, charity chiefs have revealed.
Mark Goldring, Oxfam GB's chief executive, said 16 of the claims stemmed from abroad, while 10 came from the UK.
Giving evidence to the Commons International Development Committee, Mr Goldring said around 7,000 people have cancelled regular donations to Oxfam over the past 10 days, adding that corporate sponsors appeared to be "reserving judgment".
Mr Goldring publicly apologised for the actions of charity staff who sexually exploited female victims of the 2010 earthquake in Haiti.
And he also apologised for his own comments which appeared to play down the seriousness of the scandal, when he told a newspaper that the charity was being attacked as if it had "murdered babies in their cots".
The parliamentary hearing comes in the wake of the news of resignations and dismissals of Oxfam staff in Haiti following allegations of "sex parties" involving prostitutes.
Asked how many more revelations had come to his notice since newspaper reports of the Haiti scandal emerged earlier this month, Mr Goldring said: "Across Oxfam Great Britain we have had about 26 stories, reports come to us which were either new reports come out as a result of the stories, or earlier stories where people said, 'I didn't necessarily report this at the time'. Over an extended period of time, I am not talking about recent cases.
"We really want people to come forward wherever they are and whenever this happened. Some of those cases relate to the UK, some of them relate to our international programme."
Mr Goldring apologised after committee chairman Stephen Twigg said that the parallel the charity chief drew with the murder of babies in an interview with the Guardian was regarded by many people as "grossly inappropriate".
Mr Goldring responded: "I do apologise. I was under stress, I'd given many interviews, I'd made many decisions to try to lead Oxfam's response to this. I was thinking about amazing work I've seen Oxfam do across the world, most recently with refugees coming from Myanmar.
"I should not have said those things. It is not for Oxfam to judge issues of proportionality or motivation."
Oxfam International's executive director Winnie Byanyima told the committee: "Some hideous men came into our organisation and abused the trust of the British people, the supporters.
"But they were able to get away, to get a recommendation to leave. This was wrong."
Caroline Thomson, who became chairwoman of Oxfam's trustees in October 2017, said: "On behalf of the council of Oxfam, we are ashamed of what happened in Haiti.
"We don't think it was well handled and our task now is to make sure we report always with transparency and accountability.
"My task is to make sure we never again can be at risk of being perceived to have put reputation over accountability."
Mr Goldring told the committee Oxfam made the wrong call at the time of the original investigation into events in Haiti when it issued a press release revealing its findings of "serious misconduct" involving bullying, intimidation and breaches of the charity's code of conduct, but did not go into details about the fact that sexual exploitation was involved.
"At the time, people thought that was being transparent. We know now that that was not enough.
"My colleagues at the time made a set of decisions about how public to go. With hindsight, they made the wrong call. If we were culpable - which we were - we should have been completely transparent."
Mr Goldring said that one of those who resigned or were sacked as a result of events in Haiti was later re-employed by an Oxfam organisation elsewhere in the world - but not by Oxfam GB.
"That was a mistake," he said. "It shouldn't have happened. It was a short-term contract, but that was a failing."
Mr Goldring revealed that when another aid charity later inquired about whether it should offer a job to Roland van Hauwermeiren, who was forced to resign as a result of the Haiti scandal, it declined to offer a reference but merely listed his positions at Oxfam.
"We should have been more pro-active," said Mr Goldring. "We should have said 'Please call us - there is cause for concern'."