Accusations of sexual harassment and intimidation have been levelled at the head of a UN team praised for her role in elections in Afghanistan and Iraq.
Carina Perelli has not commented on the allegations
The allegations against Carina Perelli, head of the UN's Electoral Assistance Division, were quoted in a report commissioned by the world body.
But a UN ambassador defended Ms Perelli and said the report was preliminary.
UN peacekeepers and Secretary General Kofi Annan have also been criticised following recent scandals.
The UN commissioned the investigation into the Electoral Assistance Division after staff complained about their work environment.
The report quoted staff accusing Ms Perelli of harassment and intimidation but it did not directly blame her.
Members of her team said they had "suffered emotionally" because of her behaviour and complained they worked in an "abusive" environment full of sexual innuendo and intimidation.
Ms Perelli is said to have made sexual advances to a male colleague.
Accusations of favouritism and misuse of travel funds were also quoted in the report.
UN spokesman Fred Eckhard said the allegations in the report went beyond mismanagement.
It is up to the department head "to conduct a preliminary inquiry, which he is now doing", he said.
'An excellent servant'
Ms Perelli, who is from Uruguay, has earned recognition for spearheading the UN's involvement in the elections in Iraq, Afghanistan and the Palestinian territories.
The UK's ambassador to the UN, Emyr Jones Parry, said the report only represented initial findings and should not be taken as proof of wrongdoing.
"Perelli has been an excellent servant of the United Nations," he said. "Due process has to be followed."
Ms Perelli is preparing a response to the report, UN officials told the Reuters news agency.
An investigation into the world body's oil-for-food programme in Iraq reported on Wednesday that Mr Annan was misled by his son.
Although Mr Annan was cleared of any personal wrongdoing, his handling of the affair was faulted in the report.
In February, the head of the UN's refugee agency, Ruud Lubbers, resigned after allegations of sexual harassment.
Scandals have also dogged the world body's work in Africa, where peacekeeping soldiers have been accused of using their position to procure sex.