The White House has accused Bill and Hillary Clinton of hypocrisy over their attacks on George W Bush's decision to spare an ex-White House aide from jail.
George W Bush has not ruled out granting a full pardon to Libby
President Bush commuted the jail term of Lewis "Scooter" Libby, convicted over a CIA-leak case, on Monday.
White House spokesman Tony Snow accused the Clintons of "chutzpah" - Yiddish for brashness - in criticising Mr Bush.
President Clinton issued 140 pardons on his final day in office, including one for fugitive financier Marc Rich.
Mr Bush commuted the 30-month prison sentence but left in place a $250,000 (£124,000) fine, which Libby paid on Thursday, and a two-year "supervised release", or probation, period. He has refused to rule out a full pardon for Libby.
The president's decision has left the courts in quandary, because under US law supervised release is only available to people who have served prison time.
The White House's accusation of hypocrisy against the former president and first lady followed a radio interview in which Mr Clinton said the Bush administration viewed the law as a "minor obstacle".
Mr Clinton, from the state of Arkansas, also rejected comparisons with his own controversial granting of pardons, saying "the facts were different".
Mrs Clinton, a Democratic contender for the presidential elections in 2008, in turn accused the administration of having "elevated cronyism over the rule of law".
White House spokesman Tony Snow responded: "I don't know what the Arkansan is for chutzpah, but this is a gigantic case of it."
He then referred critics to Mr Clinton's pardons on the last day of his presidency, 20 January, 2001.
Fellow White House spokesman Scott Stanzel also attacked Democratic leaders for their "rather startling" hypocrisy over the commutation of Libby's sentence.
He accused the Clintons of gall in criticising "what we believe is a very considered, very deliberate approach to a unique case".
Democratic House Speak Nancy Pelosi has described Mr Bush's intervention as a "betrayal of trust of the American people".
Granting the commutation, which was welcomed by many Republicans, Mr Bush said it had been a "very difficult decision".
He reiterated that Libby's punishment was "severe" and said he took into consideration Libby's background and service to his country.
WHAT IS CIA LEAK CASE ABOUT?
Libby was found guilty of lying to the FBI and a grand jury over revelations about CIA agent Valerie Plame's identity
Critics said the White House leaked Ms Plame's identity to undermine her husband, ex-ambassador Joseph Wilson
He had publicly cast doubt on the Bush administration's case for war in Iraq
The alleged cover-up, rather than the leak itself, was the subject of the Libby trial
Libby's supporters have raised money towards his legal fees but he paid the $250,000 fine from his own money, a source close to the fund told the Associated Press news agency.
He was found guilty in March of perjury and obstructing justice in a case connected to Washington's decision to invade Iraq.
His trial stemmed from the accusation that the White House had illegally made public the identity of a serving CIA agent, Valerie Plame, in an apparent effort to embarrass her husband.
Ms Plame's husband, a former US diplomat, had publicly criticised the basis for the invasion of Iraq.
Libby was found to have lied to investigators about conversations where he mentioned Ms Plame, but he was not convicted of having directly leaked her name.