Haiti's President Jovenel Moise decried Oxfam's handling of a prostitution scandal in the Caribbean nation, calling the situation a "serious violation of human dignity."
The British charity has come under sharp criticism for its handling of misconduct allegations against staff members accused of using prostitutes in Haiti following a devastating 2010 earthquake.
"There is nothing more undignified and dishonest than a sexual predator who uses his position as part of the humanitarian response to a natural disaster to exploit needy people in moments of great vulnerability," Moise wrote on Twitter late Monday.
The Ministry of Planning and External Cooperation on Thursday summoned representatives of the charity in Haiti requesting explanations.
"We have learned, not without dismay, that the NGO Oxfam is implicated in juvenile sex crimes in Haiti in the aftermath of the devastating earthquake of January 12, 2010," said Minister Aviol Fleurant on Tuesday.
"The directors would have used the organization's funds for this purpose," he said, saying that in addition to "serious sexual crimes" the episode would also meet criteria for a "'crime against development' in light of the possible diversion of external aid for the use of illegal criminal activities."
Oxfam has denied covering up the scandal, which triggered the resignation of its deputy chief executive on Monday.
"As programme director at the time, I am ashamed that this happened on my watch and I take full responsibility," Penny Lawrence said in a statement.
The allegations revolve around Roland van Hauwermeiren, who was Oxfam's country director for Haiti and was previously the head of the charity's mission in Chad.
Oxfam investigated sexual misconduct allegations in 2011 and van Hauwermeiren was one of three staff members who resigned while four others were dismissed.
Investigations into the seven men examined the use of prostitutes, downloading of pornography, bullying and intimidation.