Actress Minnie Driver has resigned from her role as an Oxfam celebrity ambassador and corporate backers demanded accountability as the aid organization sought to address allegations that senior staff members working in crisis zones paid for sex among the desperate people the group was meant to serve.

The star of Good Will Hunting said she will no longer support the organization following its response to a sex abuse scandal in Haiti after its 2010 earthquake. Britain's top development official has savaged the leadership of Oxfam for its handling of the scandal.

Driver tweeted: "All I can tell you about this awful revelation about Oxfam is that I am devastated. Devastated for the women who were used by people sent there to help them, devastated by the response of an organisation that I have been raising awareness for since I was 9 years old."

All I can tell you about this awful revelation about Oxfam is that I am devastated.Devastated for the women who were used by people sent there to help them, devastated by the response of an organization that I have been raising awareness for since I was 9 years old <a href="https://twitter.com/hashtag/oxfamscandal?src=hash&ref_src=twsrc%5Etfw">#oxfamscandal</a> —@driverminnie Agreed.But, there are many other organizations with feet on the ground in developing countries,from big NGOs to grassroots.<br>No one has to stop helping because there has been terrible leadership in one area. To me,accountability can't just be a trigger word,it has to be actionable <a href="https://t.co/3PMYCyXuS2">https://t.co/3PMYCyXuS2</a> —@driverminnie

The anti-poverty organization has been reeling since the Times of London reported last week that seven former Oxfam staff members who worked in Haiti faced misconduct allegations that included using prostitutes and downloading pornography.

Oxfam says it investigated, but the government and charity regulators have criticized its lack of transparency in its handling of the matter.

U.K. Development Secretary Penny Mordaunt has warned that government funding to the group — some £31.7 million pounds (about $43.8 million US) — is at risk unless it comes clean about the allegations.

What is clear is that the culture that allowed this to happen needs to change and it needs to change now. - U.K. Development Secretary Penny Mordaunt

Amid fears that sex predators have targeted aid organizations to get access to the vulnerable, Mordaunt told a conference in Sweden that she would be meeting with the National Crime Agency on Thursday to underscore her concerns.

"While investigations have to be completed and any potential criminals prosecuted accordingly, what is clear is that the culture that allowed this to happen needs to change and it needs to change now," she said.

Oxfam's corporate partners, including Visa, Mark & Spencer, Heathrow Airport and Waterstones, are asking questions about the scandal. (Simon Dawson/Reuters)

Oxfam's corporate partners, including Mark & Spencer, Heathrow Airport and Waterstones, are asking questions.

Visa, for example, which developed a partnership with Oxfam to help distribute funds to people hit by natural disaster, said it is watching closely.

"At Visa, we are committed to the highest standards of professional and personal conduct, and we expect the same from our partners," the company said.

"We are engaged with Oxfam to understand what steps have been taken to address staff misconduct and ensure alignment with our own standards and values."