Saddam Hussein's regime made billions of dollars more than previously thought from the United Nations oil-for-food programme, US officials have said.
Oil-for-food was the UN's highest spending project
Established to help ordinary Iraqis during 12 years of sanctions, the programme was the highest-spending project ever undertaken by the UN.
But the US Treasury estimates $10bn of illicit gains were made between 1997 and 2002 from the scheme, up from $6bn.
UN Secretary General Kofi Annan has called for a full investigation.
There are also allegations that UN staff reaped money from the programme, and that oil money was used to bribe UN employees to back Saddam Hussein, according to reports.
Former Iraqi cabinet officials, legislators, activists and journalists are also accused of benefiting from the oil sales.
The oil-for-food programme allowed Iraq to sell set quotas of oil, the proceeds from which were earmarked to pay for medicine and food.
A UN embargo had prevented Iraq from selling oil after the 1991 Gulf War.
The US General Accounting Office (GAO), the investigatory arm of Congress, says Saddam Hussein earned $5.7bn from oil smuggled out of Iraq and $4.4bn from illegal surcharges he placed on oil.
GAO officials say oil was smuggled through Syria, Jordan and the Persian Gulf and that the government imposed surcharges of up to 50 cents a barrel. It also took commissions of between 5-10% from suppliers.
In order to obtain more Iraqi money stashed away by the old regime, the US Treasury on Thursday submitted the names of 16 Saddam Hussein family members and 191 quasi-governmental firms to the UN.
The scheme kept most Iraqis alive under Saddam Hussein
A UN Security Council resolution requires that member nations freeze accounts which contain Iraqi money and hand over the funds for Iraq's reconstruction.
Saddam Hussein's family was "critical to the financial workings and underpinnings of the regime," treasury official Juan Zarate said.
The GAO says the US has seized $926m of assets of the toppled regime inside in Iraq. Outside the country, about $3.7bn of assets have so far been frozen.
But the officials have said little headway has been made in uncovering Saddam Hussein's presumed secret caches of money.