This report finally demolishes the Government's case for war

The biggest blow comes late in the report, when the ISC reviews the intelligence assessments that came after the September dossier

The report of the Intelligence and Security Committee is cautious, balanced and understated. In short it has all the virtues that the notorious September dossier lacked. I am getting up a campaign for Ann Taylor for Chair of the Joint Intelligence Committee.

What always puzzled me about the September dossier was its certitude. In that respect it resembled none of the JIC assessments I used to read at the Foreign Office. They were tentative and qualified, and fairly set out the intelligence evidence on both sides of the question. The September dossier was markedly different in two key issues of tone. First its assertions were never nuanced by qualification or rational doubt. Secondly it presented a one-dimensional picture without any conflicting information. Anything that did not fit the case for war got filleted out in successive drafts.

An excellent example is highlighted in the ISC report which reveals that early drafts of the Prime Minister's foreword contained the caveat, "The case I make is not that Saddam could launch a nuclear attack on London or another part of the UK (he could not)." The ISC, with dry understatement, observes that the removal of this sentence was "unfortunate". It was also no doubt deliberate. Such a sentence would have conflicted with the alarmist agenda of the dossier.

It is not just the Government who could learn a lesson from the prose style of the ISC. Andrew Gilligan could usefully be sat down every Sunday afternoon and obliged to copy it out in longhand. It is clear from the ISC report and even more from the evidence to the Hutton inquiry that he had a point. Members of the intelligence community were unhappy that the September dossier did not present a rounded picture of the intelligence. That really should have been enough for a solid, honest item of reporting. Unfortunately, Andrew Gilligan blew it by over-sexing his own report.

I never imagined that Tony Blair thought for one minute that even the most outré claim in the September dossier was wrong. On the contrary, the root reason why Britain ended up going to war on intelligence that proved to be unreliable was that Tony Blair and those around him were so passionately convinced of the case against Saddam that they did not apply a sceptical mind to any intelligence that supported their prejudices.

The ISC report spells out how flimsy was the intelligence on which they erected their case for war. In particular, it confirms that the intelligence on the 45-minute claim was limited to battlefield munitions, and that it was "unhelpful" that this was not highlighted in the dossier. I nurse the suspicion that the authors of the dossier regarded it as helpful to leave the impression that 45-minute readiness applied to real weapons of mass destruction of longer range than the battlefield, as it increased the urgency and the alarmism of the threat. The authors of the September dossier were not naive, and knew exactly what they were doing.

The limitation of the ISC report is that it is confined to the process of producing the dossier. Its members resolved early on that their remit was not to judge whether the decision to invade Iraq was correct. But this leaves unanswered the real political issue. Why did so much of the intelligence on which Number 10 built the case for war turn out to be wrong? There were no weapons ready for use in 45 minutes, whether on the battlefield or anywhere else. There was no uranium contract with Niger. The invasion of Iraq was the first time British troops were committed to action on the basis of intelligence alone, and every major piece of that intelligence has turned out to be wrong. It appears a hopelessly inadequate response to focus only on whether the process of drafting the dossier followed correct procedure, rather than ask the much larger question why so much of it was flatly wrong.

It would be equally inadequate if the media and the Opposition now get diverted into a game of hunt the Hoon. The decisions to publish the dossier, to go to war, and to identify David Kelly were collective ones, and no single minister should be asked to carry the can. If Geoff Hoon was at fault in any particular, it was that he was too loyal in carrying out the Prime Minister's wishes and not robust enough in querying whether it was a wise policy. But this is hardly an offence for which the Prime Minister can now sack him.

The real issue over the worries of the Defence Intelligence Staff is not whether Geoff Hoon gave a full answer in evidence to the ISC, but why their concerns were not reflected in the September dossier. If true, it is astounding that the JIC never knew that Britain's leading military expert on chemical weapons was unhappy with the dossier. Nor were his reservations entirely "linguistic" as Geoff Hoon argued yesterday. The evidence published by Hutton reports the same expert commenting that the decision to claim the production of phosgene as evidence of a chemical weapons programme was "a pretty stupid mistake".

The biggest blow to the Government's case for war comes late in the ISC report, when it reviews the intelligence assessments that came after the September dossier. It reveals that in February Number 10 received a JIC assessment on Iraq and international terrorism which could not be more at odds with the Government's public position. The JIC assessed that the threat from al-Qa'ida "would be heightened by military action against Iraq". This does hole below the waterline the case advanced in both Washington and London that the invasion of Iraq was somehow part of a war against terrorism.

Unfortunately this is one JIC assessment which is proving correct after the event. The months since the fall of Baghdad have been punctuated by further audacious and violent terrorist bombings. And international terrorists, who never got over the border under Saddam, are now so prevalent in Iraq that George Bush has been obliged to designate it the new central front in the war against terrorism.

But the most embarrassing revelation is that JIC warned that the collapse of the Iraqi regime would increase the risk of chemical or biological agents finding their way into the hands of terrorists. That warning dropped on desks in Number 10 in February. One month later Tony Blair addressed Parliament on the eve of war and put at the centre of his speech the need to prevent the weapons of mass destruction of rogue states falling into the hands of terrorists. At no point in that speech did he admit that the intelligence advice to him was that the war would increase the very threat he claimed it would reduce.

The position in which Number 10 now finds themselves in relation to Iraq could hardly be more desperate. Every argument that they used to justify the war has collapsed. There was no current and serious threat from weapons of mass destruction. There is a real threat from terrorism, but it has got worse, not better, as a result of the war. The time is looming when they can no longer go on denying that the real reason they took Britain to war was not weapons of mass destruction nor terrorism, but to impress George Bush that Tony Blair was his reliable ally.