Oxfam has lost 7,000 regular donors since it was revealed that staff sexually exploited victims of the Haiti earthquake in 2010, its chief executive has told a committee of MPs, which accused the charity of treating vulnerable women “like trinkets”.

During questioning by the international development committee, Mark Goldring apologised to MPs for the actions of staff who were dismissed for their use of sex workers in Haiti, and acknowledged that the charity’s actions had damaged the whole aid community, as well as the people of Haiti.

The Labour MP Stephen Twigg, who chairs the committee, said it was striking how often Goldring needed to apologise during the near-two-hour evidence session, saying there was “a lot to apologise for”.

Goldring said there had been 26 reports of sexual misconduct since the news of the Haiti abuse broke, of which 16 related to international programmes. “We really want people to come forward wherever they are and whenever this happened,” he said.

He also admitted thousands of people had cancelled their donations since the scandal broke and said corporate donors were waiting to watch what the charity’s response would be.

On another difficult day for Oxfam, which culminated in Penny Mordaunt, the international development secretary, saying the former executives Dame Barbara Stocking and Penny Lawrence may have deliberately misled the Charity Commission, a Guardian/ICM poll of more than 2,000 people revealed the effect the scandal has had on the public perception of aid charities.

Asked people whether they were “less likely to donate to humanitarian charities such as Oxfam in the future”, 35% said they were less likely and 24% no less likely, with 32% saying they did not donate anyway. Of those who said they already donated, 52% said they would now be less likely to fund humanitarian causes.

Matthew Rycroft, the permanent secretary at the Department for International Development, told the committee that the Oxfam scandal had undermined public support for spending money on aid.

“The reputation of the sector, the reputation of aid, the reputation of the 0.7% commitment, all of those I think have been pulled into the mix,” he said. “All of those things, I think, are threatened by this crisis. But we are determined to act with you, with the charities, with the private secretary, with others to turn that around.”

Goldring, who took up his post in 2013, said Oxfam’s director in Haiti, Roland van Hauwermeiren, should not have been allowed to resign when his role in the scandal was revealed and that the charity should have done more to warn future employers rather than merely refusing to give a reference.

When pressed on the ages of the women involved, Goldring said Oxfam’s own investigations found no women were under 18, the legal age of consent in Haiti. “Our investigation included trying to speak to the women involved ... and it interviewed as many of the women as it could trace. In those interviews, the women were asked their age and no evidence arose they were under 18.”

The Conservative MP Pauline Latham said she was deeply concerned about the attitude to the Haitian women involved, including comments from Goldring that the charity had been advised not to report it to the authorities in Haiti because of a lack of confidence that any action would be taken. Goldring said he had not been able to track down where the advice had come from, “either verbally or informally”.

“Prostitutes are victims, they are not doing it because they want to be prostitutes,” Latham said. “These poor girls have had a natural disaster. You as an organisation, along with others, go in there promising to help. These are pretty vulnerable women and girls, looking for Oxfam to get them through this terrible situation. You are dealing with these women and girls as if they are just trinkets and you can pay for them, give them a bit of aid, and that’s OK.”

Goldring repeatedly apologised to the committee for his own comments that had appeared to play down the seriousness of the scandal. In an interview last week in the Guardian, Goldring said the charity was being attacked as if “we murdered babies in their cots” and said he had not slept for six days.

“I make no excuses, I make an apology for comparing what I was going through with the bigger picture,” he told MPs. “My first concern is the women of Haiti and anybody else who has been wronged as a result of Oxfam’s programme. I shouldn’t have put my own sleep, or lack of it, in the public domain.

“I have tried hard to balance work and sleep over the last two weeks. The results, I believe, are that I’m continuing to do my job and I’m continuing to make appropriate decisions. I hope I have led Oxfam competently, but that’s for others to decide.”

Goldring told the committee that at the time of the original investigation into events in Haiti, Oxfam issued a press release revealing its findings of “serious misconduct” involving bullying, intimidation and breaches of the charity’s code of conduct. It did not go into details at the time about the fact that sexual exploitation was involved. He admitted, with hindsight, the charity should have been more transparent.

Two other Oxfam officials also issued apologies on behalf of the organisation. Winnie Byanyima, Oxfam’s international executive director, said: “I have spent my life trying to stand up for women’s rights and to fight for people living in poverty. This is painful for me. 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, the chair of trustees at Oxfam, said: “On behalf of the council for 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.”

Oxfam has pledged to overhaul its recruitment and vetting procedures and submit to an independent commission to investigate allegations of sex abuse.

Twigg said the committee had agreed to launch a wider inquiry into sexual exploitation in the aid sector and said MPs would be seeking to hear from people who had been in management roles at the time of the 2010 earthquake.

Mordaunt told the Commons in a statement later on Tuesday that two former executives may have deliberately misled the Charity Commission, donors and any prosecuting authorities.

Saying that the charity had “failed under the watch of Barbara Stocking and Penny Lawrence”, she added: “Even as their report concluded that their investigation could not rule out the allegation that some of the women involved were actually children, they did not think it was necessary to report this to the police either in Haiti or the country of origin for those accountable.”

The chief executive of Save the Children, who was also questioned by the committee, said a globalised system of police checks was needed to counteract “predatory males” who insert themselves into positions of power among vulnerable people seeking food and security.

Kevin Watkins said he did not agree with the argument that the aid sector had been given a hard time in the media. “There’s only one victim in this story that is the people who have had their lives shattered. The other victim is trust.”