LONDON - Key parts of Tony Blair's evidence to the Chilcot inquiry into the Iraq war will be given in secret, sources close to the hearings have revealed.

His conversations with President George W. Bush when he was British Prime Minister, and details of the decision-making process that led Britain into war, will fall under the scope of national security and the protection of Britain's relations with the United States. But well-placed sources also suggested anything "interesting" would also be shrouded in secrecy, leaving Blair's public appearance containing little more than is known.

The revelation will dash hopes that Blair will finally detail in public why he committed British troops to the invasion on the basis of flimsy intelligence. Liberal Democrat leader Nick Clegg said if a significant proportion of Blair's evidence were held in private, the public would "rightly conclude that the inquiry is simply too weak to give us the truth".

Yesterday Blair told the BBC that he would have gone to war even if he had known Saddam Hussein had no weapons of mass destruction. He would have deployed "different arguments" to remove Saddam, Blair said - undermining his long-held case that Saddam needed to be toppled because of the threat of WMDs. "I would still have thought it right to remove him. Obviously you would have had to use and deploy different arguments, about the nature of the threat. I can't really think we'd be better with him and his two sons still in charge."

All of the evidence held behind closed doors is expected to be edited from the Chilcot panel's final report.

There are already concerns that Sir John Chilcot and his four fellow panellists have given the 27 witnesses who have so far appeared - mainly senior Foreign Office mandarins - an easy ride over their role in the war.

Former MI6 chief Sir John Scarlett, in evidence last week, distanced himself from the "overtly political" foreword to the September 2002 Downing St dossier. Yet the panel failed to ask why it was that Blair and Alastair Campbell were able to amend the document he was in charge of. Scarlett will also give evidence in private.

The inquiry adjourns for the Christmas break this week. Blair will appear in public in the new year, followed by a private session.

This year it was revealed that Blair lobbied Prime Minister Gordon Brown, through Cabinet Secretary Sir Gus O'Donnell, for the inquiry to be held in private to prevent it turning into a "show trial".

After widespread uproar, the move was blocked and it was announced all evidence would be public and televised. Yet a source close to the inquiry said yesterday that the "interesting" aspects of Blair's evidence would still be heard behind closed doors.

"Anyone who thinks the public will have their day in court with Blair is wrong." It is thought the move arose from a mutual agreement. Whitehall frequently uses national security as a reason to withhold documents from the public. The Freedom of Information Act blocks the release of details where the effects of disclosure could damage Britain's relations with any other state or international organisation.

Hans Blix, head of the UN weapons inspectorate in 2003, said Blair's confession had left a "strong impression of a lack of sincerity".