Oxfam has offered its “humblest apologies” to the Haitian government over allegations of sexual exploitation by its staff.

The chief executive of Oxfam GB, Mark Goldring, and the head of Oxfam International, Winnie Byanyima, have also requested an “official high-level meeting” with the government.

On Monday, two senior members of the charity’s leadership, Simon Ticehurst and Margalida Massot, met Haiti’s minister of planning and external cooperation to present the formal apology. The meeting was called by the minister to “begin clarifying the exact allegations and investigations” into the “abusive behaviours” of some Oxfam staff after the devastating earthquake in 2010 which killed thousands of people.

Ticehurst, who is the regional director for Latin America, said: “Oxfam is grateful to the Haitian government for allowing us the chance now to offer our humblest apologies and to begin explaining ourselves and start the long road ahead of re-establishing trust and partnership, given our 40-year history with Haiti and its citizens.

“We stand ready to engage with the Haitian people and have expressed our openness to cooperate as much as required with the Haitian government.”

The apology was made as Oxfam finally released the findings of its investigation into the behaviour of relief workers sent to Haiti in the aftermath of the earthquake, as part of efforts to draw a line under the crisis that has engulfed the charity for the past week.

Quick Guide How the Oxfam-Haiti controversy unfolded Show What happened in Haiti? Oxfam GB has been accused of covering up an inquiry into whether its staff used sex workers in Haiti in 2011 during a relief effort following the previous year’s earthquake. It is alleged those who were paid by the aid workers may have been underage. An investigation by the Times found that Oxfam had allowed three men to resign and sacked four others for gross misconduct after an inquiry into sexual exploitation, the downloading of pornography, bullying and intimidation. How much money could Oxfam lose? The UK government has threatened to cut funds to Oxfam unless it shows “moral leadership”. In 2016-17, Oxfam’s income was £408.6m, according to its annual report, including £31.7m from the DfID. Aidan Warner of the National Council for Voluntary Organisations said: “They will be concerned not just about the money but the endorsement that the relationship with DfID represents, and they are clearly working hard to regain the confidence of the government as well as the public.” How much does the DfID give to NGOs? Last year the UK government dedicated £13.3bn to international aid. About £1.2bn of UK aid is spent annually through NGOs. In 2016, the UK was one of only six countries to spend 0.7% of gross national income on aid, a target set by the UN for all developed countries. Penny Mordaunt, the international development secretary, has said the UK remains committed to this target, despite some Tory MPs calling for it to be dropped. Should other NGOs be worried? A number have now been implicated. Some of the employees involved in the Haiti case went on to work for other NGOs. Over the weekend, the Sunday Times also reported that more than 120 workers from Britain’s leading charities have been accused of sexual abuse in the past year. Save the Children, which in 2016 secured multi-year contracts worth £91m with the government, had 31 cases, 10 of which were referred to the police. The British Red Cross, which admitted a “small number of cases of harassment reported in the UK”, received £16.3m in DfID funding.

A copy of the 10-page report includes details of how the allegations came to light and of Oxfam’s investigative process, which included interviews with about 40 witnesses – one of whom was physically threatened and intimidated by three of the suspects after details of the investigation were leaked.

Responding to the report during a visit to a school in west London, Theresa May described the behaviour uncovered as “horrific”.

The prime minister told journalists: “The behaviour that we’ve now discovered was horrific. It was far below the standards that we expect for the charities and the NGOs that we’re working with. And I understand there have been further revelations today which show that actually there was physical intimidation of witnesses. This is absolutely horrific.

“This is exactly the problem that we see which means that all too often people don’t feel able to come forward to report what has happened to them, the behaviour that they’ve been on the receiving end of.”

The apology and release of the report follows a threat by Haiti over the weekend to revoke Oxfam’s permission to work in the country.