The Chilcot Inquiry into the Iraq war insisted Tony Blair would be questioned "very much in public" amid claims that key evidence from the former British Prime Minister would be heard behind closed doors.
Liberal Democrat leader Nick Clegg warned that it would be "wholly unacceptable" if anything other than the most sensitive matters relating to national security was dealt with in private.
His comments came as The Independent on Sunday reported that Mr Blair's meetings with President George Bush and details of the decision-making process that led to war would be dealt with in secret on grounds of national security and the need to protect Britain's relations with the US.
However, a spokesman for the inquiry said: "Mr Blair will be appearing very much in public and will be questioned in detail on a wide range of issues surrounding Britain's involvement in Iraq."
Under the procedures adopted by Sir John Chilcot, the retired Whitehall mandarin heading the inquiry, it is intended that most evidence will be taken in public although there is a provision for closed hearings to cover issues concerning national security or secret intelligence.
So far the only witness who it has been confirmed will give evidence in a private session is Sir John Scarlett, the former MI6 chief and chairman of the Joint Intelligence Committee who drew up the Government's controversial Iraq dossier, and who appeared in public last week.
The former Prime Minister was under fire after saying that he believed it would have been right to invade Iraq even if it had been known at the time that he did not have weapons of mass destruction.
In a BBC interview with Fern Britton, he said that other arguments would have had to be found to justify military action, but that the threat posed to Saddam by the reason had been uppermost in his mind.
Mr Clegg said it was now essential that as much as possible of Mr Blair's evidence was heard in public. "It would be wholly unacceptable for any of Blair's testimony to be held in private, except that which could directly compromise national security," he said.
Meanwhile Hans Blix, the former United Nations chief weapons inspector in Iraq, said that Mr Blair's comments suggested a "lack of sincerity" over his stated reasons for going to war.