Nobel Peace Laureate Desmond Tutu on Thursday stepped down as ambassador for British charity Oxfam in the wake of allegations of sexual misconduct by the organisation’s workers in Haiti and Chad, Reuters reported.

Former aid workers of Oxfam, one of Britain’s biggest charities, have been accused of paying for sex while on a mission to help those affected by the 2010 earthquake in Haiti. While the accusations go back to 2011, it has been in the news after the Times published a report about it last week.

The South African archbishop was “deeply disappointed by allegations of immorality and possible criminality involving humanitarian workers linked to the charity”, a statement released by Tutu’s office said. “He is also saddened by the impact of the allegations on the many thousands of good people who have supported Oxfam’s righteous work.”

With Tutu’s resignation, Oxfam has lost four of its 15 celebrity ambassadors. British actor Minnie Driver, musician Miguel Bose, and Sengalese singer Baaba Maal have also stepped down over the past week.

Tutu’s resignation came at a time when the charity faced fresh trouble, according to The Guardian. On Thursday, Oxfam admitted it had rehired a worker who had been sacked in 2011 after its investigation into the Haiti scandal. The worker was hired as a consultant for Ethiopia, according to The Telegraph.

The allegations

The Times report had said that Oxfam’s country director for Haiti, Roland van Hauwermeiren, allegedly had prostitutes over at a villa that the charity had rented for him. The report said Oxfam knew about the allegations and even launched an internal investigation that led to four aid workers being dismissed and three others, including van Hauwermeiren, resigning.

In its report about the allegations, Oxfam said “serious misconduct” had taken place in Haiti, without going into the details. After the report came out last week, Oxfam denied trying to cover up the allegations. Soon after, other reports emerged that said former employees in Chad alleged that prostitutes were repeatedly invited to the Oxfam team house, and a senior member had been fired for his behaviour in 2006. Hauwermeiren was head of Oxfam in Chad at the time.

The charity is now under threat of losing its British government funding over the allegations. Several senior staff, including its deputy chief executive officer Penny Lawrence, have already resigned.