An Oxfam employee, who was sexually assaulted by a colleague in the Philippines, was "constructively dismissed" less than a year later, a media report said on Thursday.
Aimee Santos told the Guardian that she was molested by a female co - worker in 2016, a claim Oxfam has also acknowledged and said it had blacklisted the perpetrator.
But Santos, 45, claimed the charity mishandled her case and she was forced to resign.
Oxfam, she said, had "been extremely belligerent, retaliatory and vindictive.
And they have gone after me, even when they didn't have any merit".
The Philippine national labour relations commission ruled in October 2017 that Santos had been "constructively dismissed", a work termination in which an employee has been influenced to resign.
The decision said Oxfam had shown favour to the perpetrator "whose services management needed" and then acted with "inexplicable hostility" towards Santos.
The allegations come at a time of heightened scrutiny of sexual harassment in the humanitarian field.
Oxfam revealed in October it had dismissed 22 staff members over sexual abuse allegations in the previous year.
In a separate scandal, the charity temporarily suspended its work in Haiti to investigate claims of former staff paying for sex.
At the time of Santos's assault, she was working as a gender and protection coordinator.
She did not want to open a criminal investigation, she told the Guardian.
Nor did she want to go through Oxfam's internal reporting system as she felt her managers had not supported her work and would not conduct an impartial investigation.
Instead, Santos attempted to mediate with the woman.
This "restorative justice", as it is called, is an alternative method of combatting gender - based violence in which the survivor and perpetrator voluntarily seek a resolution.
However, the method is still not widely employed in the workplace.
Oxfam said in a written response that it would not use or recommend restorative justice to deal with sexual harassment or abuse allegations.
Oxfam told the Guardian that it had "fully investigated and upheld this allegation of sexual abuse.
The perpetrator's contract ended before the investigation was completed and they will never work for Oxfam again".
The charity said it took the commission's findings "extremely seriously and will continue to seek to improve how we prevent and deal with sexual harassment, exploitation and abuse".