Tony Blair went beyond "the facts of the case" when he put forward the reasons to go to war in Iraq, doing long-term damage to British politics, Iraq Inquiry author Sir John Chilcot has said.

Sir John has remained silent on the report since its publication in July, but appeared before a committee of senior MPs on Tuesday, and said it would take many years to repair the harm the former prime minister's actions had caused.

After an inquiry lasting seven years, the Chilcot Report found that former Iraqi dictator Saddam Hussein posed "no imminent threat" at the time of the invasion of his country in 2003, and the war was unleashed on the basis of "flawed" intelligence.

Its publication led to calls for the prosecution of Mr Blair, but the former premier insisted that, while he felt sorrow for those whose loved ones died, he stood by his decision to commit Britain to the US-led military action.

Asked if trust in politics had been corroded because MPs were told things that could not reasonably be supported by the evidence, Sir John told the House of Commons Liaison Committee: "I think when a government or the leader of a government presents a case with all the powers of advocacy that he or she can command, and in doing so goes beyond what the facts of the case and the basic analysis of that can support, then it does damage politics, yes."

He told MPs he "can only imagine" it would take a long time to repair the trust.

Sir John said Mr Blair's decision to describe the threat the Hussein regime posed as imminent had been the "best possible inflection" of the evidence he had.

"A speech was made in advocate's terms and putting the best possible inflection on the description that he used," he said.

Sir John said Mr Blair had "psychological dominance" over his cabinet ministers because of his success, which meant they did not challenge him as much as they could have.

He also agreed that the ex-PM's "sofa" style of centralised, informal government could be seen as a "21st Century equivalent of Louis XIV".

He was asked by Business Committee chair Iain Wright: "Is it almost the 21st Century equivalent of Louis XIV - 'I am the state'?"

Sir John replied: "I observed what can be described in that way.

"I think it reached a high point in Mr Blair's prime ministership and I've got a memory from taking evidence from his foreign secretary, from Mr (Jack) Straw, when we asked how was it that members of the cabinet, other than Robin Cook, and to a lesser extent I suppose Clare Short, did not provide more challenge and insist on debate and insist on information."