The charity has admitted to a lack of transparency over an internal investigation about the use of prostitutes by staff in Haiti, who were there to assist the country's recovery after a 2010 natural disaster.
MSF- doctors without borders in English- have released figures about sexual harassment complaints to show transparency in the wake of the Oxfam scandal.
Roland Van Hauwermeiren, the former Belgian Oxfam worker who left his job after he was accused of using sex workers whilst responding to the Haiti quake, has spoken out for the first time.
The charity is under investigation by the Charities Commission for England and Wales.
Oxfam has denied any cover-up and said that the claims of involvement of underage sex workers were investigated internally and had turned out to be "not proven".
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.
Oxfam has come under fire after it was accused of failing to pass on information about Mr van Hauwermeiren's resignation to a French charity, which later employed him in Bangladesh.
An Oxfam spokeswoman on Wednesday said the aid agency had received 1,270 cancellations of donations by direct debit between Saturday and Monday - compared to a normal monthly average of 600.
The leading Catholic charity Cafod has sacked a staff member after it emerged that he was among former Oxfam employees accused of sexually exploiting vulnerable people in Haiti in 2011.
"The dismissal was not related to sexual misconduct and was not connected to the case in 2011, however, there were allegations of inappropriate behaviour", an Oxfam spokeswoman said. They let individuals who had undertaken criminal activity go, they did not tell prosecuting authorities; they did not tell their regulator and they did not tell their donors.
Belgium's federal prosecutors said on Thursday that they were not aware of any investigation against Van Hauwermeiren.
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.