Oxfam has been severely criticised by the Charity Commission for the way it dealt with claims of serious sexual misconduct by its staff in Haiti.
Four employees were fired after claims that prostitutes were used by staff sent to help victims of the earthquake there in 2010.
The commission said the charity failed to spot signs of a “culture of poor behaviour,” and did not report claims of child abuse.
Oxfam has repeatedly apologised.
Claims first emerged in the Times last year that employees, including former country director Roland van Hauwermeiren, used young prostitutes while based in Haiti after the earthquake.
The newspaper reported that Oxfam was aware of concerns about the conduct of Mr Van Hauwermeiren and another man when they worked in Chad before they were given senior roles in Haiti.
The Charity Commission said some of the organisation’s failings amounted to mismanagement, prompting the regulator to issue Oxfam GB with an official warning.
The report, which follows an 18-month investigation, found the charity failed to heed warnings its culture and its response to keeping people safe were inadequate.
“What went wrong in Haiti did not happen in isolation,” Charity Commission chief executive Helen Stephenson said.
“Over a period of years, Oxfam’s internal culture tolerated poor behaviour, and at times lost sight of the values it stands for.”