Former Foreign Secretary Robin Cook has urged the prime minister to draw up a strategy to withdraw British troops from Iraq.
Mr Cook said the government should plan a way to pull out troops
He said troops should be withdrawn from Iraq as soon as a democratic government was in place.
Mr Cook, who left the Cabinet over his opposition to military action in Iraq, also called on Mr Blair to distance himself from President Bush.
He made his comments in an interview for the Sunday Programme on GMTV.
Mr Cook's comments came after Mr Blair said he continued to stand "shoulder to shoulder" with the US President, insisting that now was the wrong time to "start messing around with your main ally".
Mr Cook said the prime minister's loyalty to Mr Bush was causing concern within the Labour Party, with many members unable to understand why he had allied himself so closely with "one of the most right-wing presidents we have seen in the US for a long time".
On Saturday, the US, UK, Italy and Japan said they would pull their troops out of Iraq, if asked by a new Iraqi government.
The four countries made their position clear following a meeting of the Group of Eight (G8) foreign ministers in Washington.
Mr Cook said the government should plan a way to pull out British troops.
"We really do need to get elections quickly, find a genuinely representative
government of Iraq, recognise that frankly it's not going to be sympathetic to
the coalition forces who are now so unpopular in Iraq," he said.
"And I personally think we need an exit strategy that says as soon as
elections have been held, as soon as there is a democratic government to run
Iraq, we're getting out."
Mr Cook has been critical of the US presence in Iraq in the past.
Last month he said US forces in Iraq must stop "acting like warriors and start acting like peacekeepers".