Vice President Cheney's chief of staff has been named as a possible exposer of CIA operative Valerie Plame to a syndicated columnist, according to a book by former ambassador Joseph Wilson, Plame’s husband.

In The Politics of Truth, which is published on Friday, Wilson says Lewis "Scooter" Libby is "quite possibly the person who exposed my wife's identity," according to The Washington Post’s Thursday edition, which obtained an early copy.

The vice president's office did not immediately respond to a request for comment.

Wilson writes that a "workup" of his background was done by the White House in March 2003, after his public criticism of the administration's Iraq policy.

"The other name that has most often been repeated to me in connection with the inquiry and disclosure into my background and Valerie's is that of Elliott Abrams, who gained infamy in the Iran-Contra scandal," he writes.

Wilson has also named adviser Karl Rove as a possible leaker

Another suspect named in Wilson's book: White House chief political adviser Karl Rove.

"The workup on me that turned up the information on Valerie was shared with Karl Rove, who then circulated it in administration and neoconservative circles," Wilson writes.

Columnist Robert Novak has said only that "two senior administration officials" were his sources.

Last October, White House spokesman Scott McClellan said his conversations with Rove, Libby and Abrams have ruled out their involvement.

Investigation

A federal grand jury is probing the leak of the CIA officer's identity, which is a criminal offence. Subpoenas were issued to the White House on 22 January.

The grand jury is attempting to find out if anyone violated a federal law that prohibits the intentional disclosure of the identity of an undercover agent by officials with security clearances.

Some critics have speculated that officials in the Bush administration had told reporters the name of the CIA officer to discredit her husband and his criticism of the administration's Iraq policy.

The former ambassador had been sent to investigate claims that Iraq had tried to obtain nuclear materials in Africa. Wilson said that he reported his findings - that the claims were false - to administration officials.

Wilson says his findings were ignored and President Bush later quoted the false claims about Iraq in a televised address to Americans.

Wilson says his wife was then exposed by vengeful officials after he tried to publicise the fact that his findings were dismissed.