Oxfam has confirmed it dismissed 20 members of staff over sexual abuse claims in the past year.
Two other employees at the UK charity also resigned before the investigations involving them finished.
Oxfam, based in Oxford, dealt with 87 claims of sexual exploitation and abuse in the 12 months to April 2017, up 37% on the previous year.
It said sexual abuse was a serious problem and "we all, including Oxfam, need to get better" at stopping it.
Of the complaints, 53 were referred to police and other services, Oxfam told the Thomson Reuters Foundation.
There were 33 internal investigations and about three-quarters resulted in disciplinary action.
Oxfam 'should be praised'
Megan Nobert, a campaigner who set up Report the Abuse NGO - which collected information about sexual abuse in the charity sector - said Oxfam was not alone.
She said it was a "big problem" for the humanitarian community and argued the charity was "unique" in how transparent it was being and "should be praised".
A spokesperson from Oxfam said her complaint was investigated but could not be proved.
The investigations in the year to April 2017 related to complaints by staff about other employees, they added.
In a statement the charity said more people were coming forward as a result of raised awareness.
The figures have emerged at the same time as allegations about abuse in British politics and Hollywood have come to light.
Oxfam said "high-profile cases" had "shone light into this very dark corner of society" and provided a chance to do more to tackle it.