Bush refuses to explain to Congress why he commuted prison sentence of Lewis "Scooter" Libby

President George W. Bush has refused to explain to Congress why he commuted the prison sentence of former White House aide I. Lewis "Scooter" Libby.

The husband of the CIA agent outed in the case testified during a House hearing that the clemency grant had cast a pall of suspicion over the presidency.

In a letter to House Judiciary Committee Chairman John Conyers, Bush counsel Fred Fielding said Congress had no authority to review a presidential clemency decision.

"To allow such an inquiry would chill the complete and candid advice that President Bush, and future presidents, must be able to rely upon in discharging their constitutional responsibilities," he wrote Wednesday.

The letter came in the middle of a politically charged hearing by the Judiciary panel on Bush's move last week to erase Libby's 2 1/2-year prison sentence. Libby, a former top aide to Vice President Dick Cheney, was convicted of obstructing justice in a federal probe of the leak of former CIA agent Valerie Plame Wilson's identity.

When he issued the commutation July 2, Bush said in a statement that he respected the jury's verdict but thought the prison term was too harsh.

The hearing's star witness was her husband Joseph C. Wilson IV, a former diplomat whose 2003 newspaper column challenging Bush's case for the Iraq war precipitated Plame's unmasking and the resulting investigation that ensnared Libby.

"In commuting Mr. Libby's sentence, the president has removed any incentive for Mr. Libby to cooperate with the prosecutor. The obstruction of justice is ongoing, and now the president has emerged as its greatest protector," Wilson testified.

Wilson said Bush "at the very least owes the American people a full and honest explanation of his actions and those of other senior administration officials in this matter, including but not limited to the vice president."

Conyers said he recognized Bush's constitutional right to grant clemency, but he argued that using the power to benefit a former aide who was in a position to incriminate other administration officials was suspect.

Even President Bill Clinton's pardon of fugitive financier Marc Rich "did not involve someone who worked in the White House and could potentially implicate others there, as may be or appears to be the case in this instance," Conyers said.

Democratic Rep. Jerrold Nadler compared the commutation to the pardons issued by President George H.W. Bush in the Iran-Contra affair, arguing that both excused actions that "frustrated a legitimate investigation, and the pardons guaranteed ... that that investigation could go no further."

Republicans angrily derided the hearing as a partisan stunt that could accomplish nothing, since the president has inherent constitutional authority to pardon or grant clemency to whomever he wishes.

"What's going on here today is more braying at the moon by my friends on the other side of the aisle, who spend more time looking into real or imagined misconduct on the part of the Bush administration, rather than doing the job that we were elected to do," said Sen. F. James Sensenbrenner.

Rep. Dan Lungren said Democrats were right that Bush might have handled the matter differently, but added: "The big difference is, he's the president and you're not, and he made the judgment to exercise his constitutional authority the way he did."

At one point the hearing degenerated into name-calling, as Republican Rep. Darrell Issa accused Plame of lying to the Judiciary Committee during testimony in March when she said she had not tapped her husband to travel to Niger for the fact-finding mission that led to his op-ed questioning Bush's Iraq war claims.

"This is yet a further smear of my wife's good name and my good name," Wilson loudly protested later, as Issa objected repeatedly and Conyers fought to gain control of the hearing.