Blair must be held accountable in "court of public opinion" over Iraq war, says Cameron

The former First Minister said he did not understand, in light of that remark, how it was “in any way compatible with what was said to Parliament and people at the time”.

The Gordon MP added: "Amid all this stuff about improving processes, which is fantastically important and I acknowledge it, is it not at the end of the day people who make decisions and, in our search for responsibility, wouldn't it help if individuals responsible were held accountable?"

Senior Tory MP, David Davis, picked up on another part of the memo, saying: “Later on…it says: 'The reason for this is getting rid of Saddam Hussein,[it] is the right thing to do.' Regime change, not WMD...This actually amounts to a deceit and a misleading of this House of Commons.”

He added: “Sir John has been very careful about avoiding accusing the previous prime minster of lying to the House but a lot of the evidence here suggests he did."

Mr Cameron said everyone would have to read the report and "come to their own conclusions" and added: "From my reading of it, Sir John Chilcot is not accusing anyone of deliberate, explicit deceit."

Jeremy Corbyn, who was a staunch opponent of the Iraq war at the time, condemned the decision to invade, branding it an "act of military aggression launched on a false pretext," that had long been regarded as illegal by most international legal opinion. But during some of his contribution he was heckled by his own MPs.

Denouncing the war as a “catastrophe,” the Labour leader said it had "fuelled and spread terrorism" instead of improving security at home and abroad.

Mr Corbyn also said many MPs, who had opposed the war had not lived to see themselves vindicated, mentioning in particular the late Robin Cook, who resigned from the cabinet over the decision to invade.

Mr Cameron said all those MPs, including himself, who had voted for the war had to “take our fair share of the responsibility,” but he pointed out: "We cannot turn the clock back but we can ensure that lessons are learned and acted on."

The PM made clear taking the country to war should always be a last resort and should only be done when all credible alternatives had been exhausted.

But he also argued that there were times when it was right to intervene while acknowledging that no government could ever guarantee military success, even when the necessary questions surrounding "machinery of government, proper processes, culture and planning" had been answered.

Angus Robertson for the SNP noted how the Iraq War had damaged the reputation of the UK Parliament and Government and had "left an indelible stain on Britain's standing in the world".

He asked: "When will the UK Government, of either Tory or Labour hue, actually start learning from the mistakes of the past so we are not condemned to repeat them?"

Tim Farron, the Liberal Democrat leader, said the report had made clear Mr Blair’s “absolute determination…to pursue war in Iraq no matter the evidence,” and he called on all those who had branded the late Charles Kennedy, who had led his party in opposing the war, an appeaser now to apologise.

Labour backbencher Ann Clwyd, who voted for the war and was the human rights envoy to Iraq from 2003 until 2010, stressed how Saddam was a tyrant, who had slaughtered his own people and had been in breach of a string of UN resolutions.

“The horrors of Saddam Hussein and what he did to his own people...were clearly documented. We were right to take part in that invasion."

Green MP Caroline Lucas said while MPs had lined up to criticise Mr Blair - "all of it justified" – she called on Mr Cameron to reflect on his own party's decision to back the war and apologise.

But the PM said the Brighton MP might wish to “replay all of the arguments of the day” but insisted there was little point in that.

MPs, he said, had “listened to arguments, made decisions, made them in good faith; they can now reflect on whether they think those decisions were right or they were wrong".