MSF- doctors without borders in English- have released figures about sexual harassment complaints to show transparency in the wake of the Oxfam scandal.
"Hiring Singh, even in an emergency as a short-term consultant, was a serious error and should never have happened".
The scandal has led to the resignation of Oxfam's deputy head and has thrown into question government funding for the charity, which amounted to around £32 million (36 million euros, $44 million) a year ago.
The retired South African church leader said he was stepping down as a global ambassador for the charity, saying he was "deeply disappointed by allegations of immorality and possible criminality" by some Oxfam staff.
Ms Evans said that staff had been accused of rape and that sexual abuse by shop managers in United Kingdom stores against young volunteers was covered up.
Mr Van Hauwermeiren said there had been "a lot of lies and exaggerations" about his time in Haiti.
Four members of Oxfam staff were dismissed and three, including van Hauwermeiren, left before the investigation had completed.
"They let perpetrators go".
Chris Bain, Cafod's director, said: 'The Times newspaper on 10 February wrote that a current Cafod employee was named as an Oxfam staff member who had been working in Haiti in 2011, amidst accusations of sexual misconduct'. "They did not inform donors, their regulator or prosecuting authorities", Mordaunt said.
"We requested and yesterday received a reference from Oxfam GB headquarters which confirmed the allegations against him", CAFOD director Chris Bain said in a statement.
Roland van Hauwermeiren, who is said to have resigned before the end of Oxfam's investigation into the Haiti allegations, spoke out in an interview with local media in his native Belgium.
Actress Minnie Driver has stepped down as one of Oxfam's global ambassadors following revelations of sexual abuse by aid workers in Haiti.
Several sponsors and partners of Oxfam including Visa and the retail chain Marks and Spencer have also said they are examining the situation.