The anti-poverty organization has been reeling since the Times of London reported last week that seven former Oxfam staff members who worked in Haiti faced misconduct allegations that included using prostitutes and downloading pornography.
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.
"There are things correctly described", he said, without explicitly elaborating on what he felt was untrue.
A statement from the 86-year-old to The Telegraph read: "Archbishop Emeritus Desmond Tutu has supported Oxfam International's good work for many years, most recently as one of its global ambassadors". Parties every week? Chic villas? "It's especially hard that my family doesn't want to see me anymore".
In his letter, Allan, who took over the brief from Humza Yousaf two years ago, cites allegations of "serious misconduct and sexual abuse by staff working in the global development sector, specifically in relation to vulnerable groups".
On Thursday‚ the ex-director at the centre of the scandal‚ Roland van Hauwermeiren‚ admitted some of the claims were true‚ but that there were lies and exaggerations.
The Paris-based group, known by its French acronym MSF, said it had received 146 complaints or alerts previous year, of which 40 were found to be allegations of harassment or sexual assault.
The charity, which is headquartered in Geneva, said it had received a total of 146 complaints in one year, 40 of which involved harassment or abuse.
"After an internal investigation, 40 cases were found to be allegations of harassment or abuse", the charity said in a statement.
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.
Senior staff have already left the charity.
Ms Mordaunt said: "No organisation is too big, or our work with them too complex, for me to hesitate to remove funding from them if we can not trust them to put the beneficiaries of aid first".
Meanwhile, a recent Channel 4 News interview has seen former Head of Safeguarding Helen Evans allege that abuse and sexual assault had even been reported by volunteers at shops in the United Kingdom, and that her efforts to highlight these issues were repeatedly ignored.