Senior leaders of British aid organization Oxfam are to meet government officials Monday amid warnings it could lose public funding over allegations its staff hired prostitutes in Haiti.

Ahead of the meeting, Oxfam announced it would strengthen its staff vetting procedures and introduce a new whistleblower helpline as part of a package of reforms.

"It is not sufficient to be appalled by the behaviour of our former staff -- we must and will learn from it and use it as a spur to improvement," Oxfam's chair of trustees, Caroline Thomson, said in a statement.

The aid agency has come under fire after an investigation by The Times newspaper in London revealed allegations that Oxfam's leaders tried to cover-up sex crimes by senior employees after the devastating 2010 quake, which killed hundreds of thousands of people.

The aid workers, including the Oxfam country director at the time, Roland van Hauwermeiren, were accused of turning the villa rented by the charity into a makeshift brothel, with prostitutes only wearing Oxfam T-shirts.

On Sunday, the aid agency said it had been "shocked and dismayed" to hear more allegations about the use of sex workers by Oxfam staff in Chad in 2006.

"While we can't corroborate the information from Chad at the moment, it highlights again unacceptable behaviour by a small number of people and the need for a sector-wide approach to tackle the problem," Oxfam said in a statement.

Britain's International Development Secretary Penny Mordaunt warned Sunday Oxfam could lose millions of pounds in public funding due to the scandal.

"If the moral leadership at the top of the organization isn't there, then we cannot have you as a partner," Mordaunt told the British Broadcasting Corporation's Andrew Marr. Last financial year, Oxfam received about £32 million (about $44 million) from the government, according to public records.

Oxfam's own policy prohibits "sexually abusive or exploitative acts being perpetrated" by employees, including paying for sex.

Oxfam is one of the largest UK's most prominent aid organizations, working across the globe to help people after emergencies and disasters. It calls itself "a global movement of millions of people who share the belief that, in a world rich in resources, poverty isn't inevitable."

A second report by The Times on Saturday said Oxfam failed to warn NGOs about the allegations, allowing some of the accused to get jobs at other aid agencies.

A second report

The UK Charity Commission told CNN in a statement that Oxfam informed them in August 2011 it was conducting an internal investigation related to inappropriate sexual behaviour, bullying, harassment and the intimidation of staff. But Mordaunt said the aid organization failed to reveal the scope and key details of the case.

"They let individuals who had undertaken criminal activity, they let them go. They did not tell prosecution authorities, they did not tell their regulator and they did not tell their donors," Mordaunt told the BBC.

Mordaunt's predecessor, Priti Patel, shared similar concerns about a cover-up in an interview with Sky News.

"I did my own research and I have to say I had a lot of push-back within my own department ... that is the scandal", Patel said, according to Sky. "People knew about this," she said.

Patel, who resigned last year after her secret trip to Israel and undisclosed meetings with Israeli officials set off a political firestorm, also said that British nationals accused of wrongdoing while doing charity work abroad with public funds should be tried in the UK.

"These revelations are absolutely despicable, and it highlights the extent of the abhorrent abuse that has taken place around the world within the aid sector when it comes to vulnerable people and children, and that is just unacceptable," Patel said.

Oxfam denied allegations of a cover-up Friday, saying that as soon as it became aware of the allegations it launched an internal investigation, after which four people were fired and another three resigned, including van Hauwermeiren.

"Our primary aim was always to root out and take action against those involved and we publicly announced, including to media, both the investigation and the action we took as a result," Oxfam said in a news release responding to the Times story.