Mr Blair will remain on the defensive over Iraq until he apologises to the nation

At one of the stormiest and most bad-tempered sessions of Prime Minister's Questions of recent memory, MPs challenged Tony Blair again about his fundamental arguments for the war

Any hopes the Prime Minister might have nurtured that the political furore over the Iraq war would die down after the party conference season were comprehensively dashed yesterday after one of the stormiest and most bad-tempered sessions of Prime Minister's Questions of recent memory. Back and forth MPs went, challenging Tony Blair yet again about his fundamental arguments for the war. It was no good loyal Blairites trying to shield their leader with diversions about unsuitable material on the internet or even about the European Constitution. The mood of the House was ugly. The leaders of the Opposition parties were as uncompromising as Opposition leaders should be.

Mr Blair stuck adamantly to his party conference script, with one tiny, but significant emendation. He had told his party: "I can apologise for the information being wrong" (but he did not). Now he is apologising, but only for the wrong information - not for the misleading way in which the intelligence was presented to the House, not for ousting Saddam Hussein without adequate plans for the aftermath, and certainly not for the war.

But Mr Blair was audibly and visibly on the defensive, as well he might have been. Consider the developments of the past week. The US-appointed Iraq Survey Group - the group whose report Mr Blair kept telling us we should wait for - found there were no weapons of mass destruction in Iraq before the US and British invasion, so all that the Prime Minister had told us about Saddam's possession of weapons was now acknowledged to be wrong. Within 24 hours, we learnt that Kenneth Bigley, the British engineer held hostage in Iraq, had been murdered three weeks after his abduction.

On Monday, the Foreign Secretary told us in an unannounced Commons statement, that another two key points of the intelligence on which the case for war rested had been withdrawn - what an innocent word, as if intelligence could be "withdrawn". The first was the notorious detail about the 45-minute deployment time for "some" of Saddam's weapons. The source for that eye-catching point, which had led many of the newspapers and television bulletins when the first Iraq weapons dossier was released, is now discredited. Mr Straw also noted that intelligence about Iraq's biological weapons production had also been "withdrawn". Some intelligence.

Mr Blair and his ministers have treated this torrent of bad news as though it is all rather a pity, but nothing disastrous. But how much more wrong can any piece of intelligence be. And how much more wrong can a politician's judgement be if he deems such intelligence a reasonable basis for war? An apology for this ill-conceived use of military force is the very least this country deserves, and Michael Howard is right to press for it.

But a full apology is also the last thing Mr Blair appears inclined to give.

We have now had three senior officials, Patricia Hewitt, Jack Straw and Lord Falconer, saying a public "sorry" - but not for the war. Why has the Prime Minister himself been so reluctant to use the word "sorry", delegating even this highly circumscribed regret? And why were we suddenly treated yesterday to a new and especially emotive report about the discovery of mass graves in Iraq? As with previous such finds, the graves went back to a time when Saddam enjoyed the generous patronage of the West. All mass killings are utterly despicable - but so are the propagandistic purposes for which they can be used.

It was Charles Kennedy, who most discomfited Mr Blair yesterday when he returned to the legality of the war. Either it was about banned weapons, he said, or it was about regime change, and if it was about regime change, it was illegal. He was right.

Exasperated by the renewed challenges, Mr Blair finally told the Opposition to "stop playing political games with this issue". But this is no political game. It is politics for real, and as a real political issue of high seriousness, the Iraq war is not going away.