Saddam Hussein's regime made more than $21.3 billion in illegal revenue by subverting the U.N. Oil-for-Food program (search) through surcharges, kickbacks and smuggling oil — more than double previous estimates, according to congressional investigators.

The figures are based on troves of new documents obtained by an investigative panel of the Senate Committee on Government Affairs (search), which was presenting them at a hearing Monday in Washington. The documents illustrate how Iraqi officials, foreign companies and sometimes politicians allegedly contrived to funnel vast illicit gains to the Iraqi government.

The findings also reflect a growing understanding by investigators of the intricate schemes Saddam used to buy support abroad for a move to lift U.N. sanctions.

In one document, a letter obtained by investigators, Russian ultra-nationalist politician Vladimir Zhirinovsky (search) — who campaigned for the lifting of sanctions on Iraq — invites an oil company to negotiate a price for an oil allocation the Iraqi government awarded him.

"Saddam Hussein attempted to manipulate the typical oil allocation process in order to gain influence throughout the world," Mark L. Greenblatt, a counsel for the Senate panel's permanent subcommittee on investigations, said in prepared testimony obtained by The Associated Press.

"Rather than giving allocations to traditional oil purchasers, Hussein gave oil allocations to foreign officials, journalists, and even terrorist entities, who then sold their allocations to the traditional oil companies in return for a sizable commission."

The reference to terrorist groups referred to evidence that the regime had allocated oil to such organizations as the Popular Front for the Liberation of Palestine, and the Mujahadeen Khalq, a group seeking to overturn the government of Iran, Greenblatt said.

Previous estimates — one from the General Accountability Office and the other by the top U.S. arms inspector Charles Duelfer (search) — concluded that Saddam's government brought in $10 billion illicitly from 1990 to 2003, when sanctions were in place.

But congressional investigators found that vastly more oil — totaling $13.7 billion — was smuggled out of Iraq than previously thought. Investigators also raised the GAO's estimate of $4.4 billion in Oil-for-Food kickbacks by $200 million, and said the regime made $2.1 billion more through a scheme where foreign companies imported flawed goods at inflated prices.

According to the documents, the Iraqi government signed deals to import rotting food and other damaged goods with the full understanding of the exporting companies, who accepted payments for top quality products while kicking back much of the price difference to the Iraqi regime.

The panel estimated that such substandard goods accounted for 5 percent of all goods imported under the oil-for-food program, which was put in place in 1996 amid concerns that the Iraqi population was suffering from lack of food and medicines under the sanctions. The rough estimate "is drawn from anecdotal information provide by officials of the former Iraq regime, the United Nations, and U.S. government officials," the panel said.

The total estimate of illegal revenue also includes $400 million from interest earned from hiding illicit funds in secret bank accounts. Another $400 million in illicit revenue grew out of pricing irregularities and kickbacks in the Kurdish areas of northern Iraq.

The Senate panel is conducting one of several congressional probes into alleged illegal profiteering in the Oil-for-Food program after allegations of corruption came to light earlier this year when Saddam was driven from power during the U.S.-led invasion. Former U.S. Federal Reserve Chairman Paul Volcker heads a panel that's conducting an independent investigation.

Zhirinovsky and other foreign officials and political figures implicated in the scandal so far — mostly from Russia, France and China — deny any wrongdoing.

The new documents offer examples of how Saddam's regime — sometimes the former Iraqi president himself — awarded lucrative oil allocations to garner political favors.

In Zhirinovsky's case, the Russian allegedly used his political party's letterhead to invite an international oil company to Moscow to negotiate a deal to buy oil allocated to him.

"It is my honor to invite you for negotiations to Moscow, from the 18th to the 25th of January 1999. Will be happy to meet with you," he writes, according to investigators.

The Iraqi government allocated 80 million barrels of oil to Zhirinovsky and his party, according to the panel, at a time when the Russian politician was backing Baghdad publicly.

"When Hussein kicked out weapons inspectors in the late 1990s and the U.S. threatened military action in response, Zhirinovsky pushed Russia to provide military support to Iraq," Greenblatt said in prepared testimony.