Gordon Brown and Nick Clegg traded blows over the Iraq inquiry in the Commons
Gordon Brown is facing calls to give evidence to the Iraq Inquiry before the general election.
Lib Dem leader Nick Clegg said people were "entitled" to know Mr Brown's role in the decision to go to war before voting, as he had "signed the cheques".
The Tories also said it would be "preferable" for him to give evidence to the inquiry before the election, rather than after it as planned.
Mr Brown said he was acting on the inquiry's recommendations over timings.
He also told MPs that he "stood by" the decision to go to war.
'Signed the cheques'
Former Downing Street spokesman Alastair Campbell told the inquiry on Wednesday that Mr Brown, as chancellor, had been one of the ministers Tony Blair consulted most closely on Iraq.
Evidence hearings with Mr Brown and a handful of other current ministers are scheduled to take place after the general election - expected in May.
But critics say the prime minister should appear before the country goes to the polls.
In the Commons, Mr Clegg said Mr Brown was not merely "in the room" when the UK decided to go to war but had "signed the cheques" for the 2003 invasion.
I will follow the recommendations of the Chilcot inquiry
The public had a right to know soon about his role in the "disastrous" decision to go to war, he added.
"This isn't just a question for Sir John Chilcot, it is a question for the prime minister's own conscience. He should insist on going to the inquiry now."
In a letter to Mr Brown, Mr Clegg said Mr Campbell's evidence meant "your personal role in the decisions that led to the war in Iraq has now come under the spotlight".
He added that "the sense that you have been granted special treatment because of your position as prime minister will only serve to undermine the perceived independence of the committee".
'Nothing to hide'
For the Conservatives, shadow foreign secretary William Hague said he thought it would be "far preferable" for Mr Brown to appear before the election.
But, speaking at prime minister's questions, Mr Brown said the arrangements for his appearance were a matter for the inquiry, as it was an independent body.
"I will follow the recommendations of the Chilcot inquiry," he said, adding that he had "nothing to hide".
"This is a full inquiry being run by Sir John Chilcot. People are being interviewed, rightly so, and asked for their evidence, but it is for the Chilcot committee to decide how they proceed and that is what he (Mr Clegg) proposed."
Asked about his views on the war and its aftermath, Mr Brown said he agreed with the view that planning for the reconstruction of Iraq had been "insufficient".
But he said he backed all the decisions taken by the Blair government in the run-up to the invasion.
A spokesman for the Chilcott inquiry said there were "no plans to invite Mr Brown to give evidence before the general election".
During his five-hour evidence session on Tuesday, Mr Campbell also said Mr Blair had written privately to President Bush in 2002, assuring support for military action if diplomatic efforts to disarm Iraq failed.
This led to calls for private correspondence between the two leaders, obtained by the inquiry, to be published.
Meanwhile, former cabinet secretary Lord Turnbull told the inquiry on Wednesday that key decisions about Iraq had been taken in the summer and autumn of 2002.
He said ministers believed they had pulled off a "major triumph" in September 2002 - when he took up his role - in persuading Washington to go to the United Nations for a resolution calling on Iraq to disarm.
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