Oxfam received £31.7 million in taxpayer funding in 2016/17.
Several senior officials with the worldwide charity have resigned in the wake of the controversy, including the deputy chief executive of Oxfam Great Britain.
"I'm really inviting anyone who has been a victim of abuse by anyone in our organisation to come forward".
In a statement, the British-based aid group said, "We are committed to proving that we deserve the confidence of the United Kingdom public".
Reports that Oxfam staff members sexually exploited people in crisis zones are "a stain" that shames the charity, the organisation's chief said in an interview broadcast Friday.
"From the bottom of my heart, forgive us, forgive Oxfam", the Ugandan director said in her native tongue, Luganda.
The executive director of Oxfam, one of the leading worldwide relief organizations in the world, has apologized and asked forgiveness in the wake of allegations that a former director hired prostitutes in disaster zones.
The allegations relate to Oxfam GB, one 20 affiliates that make up Oxfam International.More news: EPL: Liverpool humble Southampton 2-0, move to 3rd place
"I think (her criticism) was very unbalanced, and ironically didn't give enough credit to the very work that she promoted", he told the paper.
Van Hauwermeiren was moved to Haiti in the wake of the 2010 quake. The aid group is under fire for supposedly failing to tell the British government's Charity Commission the full story regarding the purported behavior.
'That they report staff members involved in this incident to their respective national governments; and that they fully cooperate with the Haitian authorities, including handing over all evidence they hold.
Oxfam says it investigated the case, fired four workers and let three others resign, but the British government and charity regulators have criticized its lack of transparency.
The charity admitted yesterday it rehired one of those sacked in Haiti just months later and is now checking whether any complaints were subsequently made.
The charity on Friday said it was also investigating allegations of sexual misconduct at a hotel in the Philippines after a destructive typhoon in 2013.
In response, Oxfam said it would create a global database of accredited referees to crack down on forged or unreliable references from past or current employees.
At home and overseas, we will not stand for any kind of harassment of staff, partners, volunteers or those we serve and we are doubling the number of people who work on safeguarding to make sure we are living up to our responsibility to protect them.