The former head of the UN oil-for-food programme for Iraq, Benon Sevan, has been charged with bribery and conspiracy to commit fraud by the US.
Benon Sevan headed the oil-for-food programme from 1997
Mr Sevan allegedly accepted $160,000 (£81,500) from Baghdad to illegally influence the $64bn programme.
In a statement issued via his lawyer, Mr Sevan said the charges were trivial and without basis. If convicted he could face up to 50 years in prison.
The 69-year-old Cypriot is charged along with another man, Ephraim Nadler.
Mr Nadler, 79, a brother-in-law of former UN Secretary General Boutros Boutros-Ghali, is accused of channelling kickbacks between the Iraqi government and Mr Sevan.
If found guilty, he could also face a lengthy jail sentence.
Mr Sevan countered the allegations on Tuesday, saying he had accounted for every penny as he successfully ran the largest humanitarian programme in UN history, helping to save "tens of thousands of innocent people from death by disease and starvation".
"The United States attorney's office has decided to use Mr Sevan as a scapegoat and a distraction from the United States' own massive failures and mismanagement in Iraq," a statement read.
Mr Sevan, who worked for the UN for four decades, resigned in August 2005, after independent investigators accused him of receiving money in return for helping a company obtain lucrative oil contracts.
At the time he criticised former UN Secretary General Kofi Annan for "sacrificing" him as he faced an inquiry into the scandal-ridden programme.
US attorney Michael Garcia said that the US had lodged warrants for the arrest of both men and would seek their extradition to the US for prosecution.
The oil-for-food programme, set up in 1996, was intended to allow Iraq to sell its oil in return for humanitarian relief, so it would not breach sanctions imposed after the first Iraq war.
It was formally ended in 2003 after the US-led invasion of Iraq and the overthrow of Saddam Hussein.
The BBC's UN correspondent, Laura Trevelyan, says the corruption allegations that engulfed the programme have made it the biggest financial scandal in the organisation's history.
A spokesman for UN Secretary General Ban Ki-moon said the body "reiterates the commitment to have the United Nations uphold the highest ethical standards".