UN Secretary General Kofi Annan has ordered disciplinary proceedings against the head of the oil-for-food programme in Iraq, Benon Sevan.
Kofi Annan thanked Paul Volcker for judging by the "highest standards"
The move came after an independent report accused Mr Sevan of unethical conduct undermining the UN's integrity.
Inquiry head Paul Volcker revealed in the initial findings by his panel that Mr Sevan repeatedly asked Iraqis to allocate oil to a particular company.
Mr Sevan denies any wrongdoing and said he was being made a scapegoat.
The defunct scheme let Iraq sell oil to buy food and medicine to ease the effects of international sanctions.
It ran from 1996 to 2003.
Among the complaints about the controversial programme are claims that Saddam Hussein might have diverted part of the money for his own uses.
'Conflict of interest'
Mr Annan said in a statement following the report that he stood by a pledge made when the panel was set up that no-one found to have broken the law would be shielded from prosecution.
He would waive a member of staff's diplomatic immunity if criminal charges were pursued against them, he added.
Mr Annan said that disciplinary measures had already been taken against Mr Sevan and Joseph Stephanides, currently head of Security Council affairs.
Measures had also been taken to remedy defects in the initial procurement process for companies to carry out banking and inspection services, he said.
Mr Volcker was appointed last April to investigate the allegations of corruption. His final report is expected in June.
The interim report by the independent team said Mr Sevan had "seriously undermined the integrity of the United Nations" by asking for allocations of oil on behalf of the African Middle East Petroleum Company.
Iraqi officials had agreed in a bid to secure Mr Sevan's support on issues such as funding to rebuild Iraq's oil installations, the report said.
The scheme was supposed to ease the burden of sanctions on Iraqis
Mr Sevan's conduct was "ethically improper", Mr Volcker told reporters in New York.
He "created a grave and continuing conflict of interest", the former US Federal Reserve chairman added.
Correspondents describe Mr Sevan as a veteran UN employee who has served in many of the world's trouble spots.
The Cypriot joined the organisation in 1965 and served in a variety of posts before his appointment as Executive Director of the Iraq Programme in 1997. He has now retired.
Separate inquiries are under way in the US Senate and by the Iraqi interim government.
An additional report on the secretary general and his son will be published later.
Mr Annan's son, Kojo, worked for a firm involved in the programme.