The claims of sexual abuse were first published a year ago and resulted in more than 7,000 people cancelling their donations.
This forced Oxfam to make £16m of cuts to its aid projects worldwide.
Within three days of The Times newspaper first publishing the claims, a total of 1,200 people cancelled their direct debits.
Stephanie Draper runs BOND, the UK's network for organisations working in international development, and said she felt "mortified" after hearing about the allegations.
She told Sky News: "One of the things that was particularly horrifying was that perpetrators were able to move between jobs.
"We have been working really hard across the sector in an unprecedented manner to find ways of dealing with abuse effectively.
"It's really important that if people are experiencing any sort of abuse or harassment or bullying, that they are able to have somewhere to report it."
Oxfam held its own investigation in 2011 which resulted in four people being sacked and three others resigning.
In a statement, Oxfam said: "We are committed to improving our safeguarding and culture, and have taken action to address our past failings, including tripling our investment in safeguarding and ensuring that all staff participated in code of conduct and safeguarding training.
"We have appealed for people who have any concerns to come forward."
The Charity Commission will release the findings of its investigation later today.