"There is missing money, we do not know where it has gone," Osama al-Nujaifi said at a news conference in Baghdad. "The money is around $40 billion in total."

"It may have been spent somewhere, but it does not appear in our accounts, so parliament will investigate where this money has gone."

Nujaifi did not say when or how the discovery had been made regarding the missing money. He said two investigative committees had been formed to track down the cash.

The Development Fund for Iraq (DFI), which was set up after the 2003 war to handle oil and other revenues, has been protected against claims by a UN resolution that expires on June 30.

On December 15, the UN Security Council ended key international sanctions imposed on Iraq following now-executed dictator Saddam Hussein's 1990 invasion of Kuwait in a major move toward bringing closure on the Saddam era.

Among the decisions taken on that day was the closure of the DFI.

Iraq's August 2, 1990 assault on Kuwait was rapidly met with a concerted international military response that pushed Saddam's forces out of the oil-rich emirate and eventually ended in his ouster by a US-led coalition in 2003.