The spymaster who drew up the British government's notorious Iraq dossier appeared yesterday to distance himself from Tony Blair's claim that intelligence had established "beyond doubt" that Saddam Hussein had weapons of mass destruction.

Sir John Scarlett, who was the chairman of the Joint Intelligence Committee, the senior UK intelligence body, described Mr Blair's comments in the foreword to the dossier as an "overtly" political statement.

Giving evidence to the official inquiry into the war, Sir John - who went on to become the Chief of the Secret Intelligence Service, MI6 - said he did not see the foreword as something which he could alter.

"I saw the foreword as quite separate from the text of the dossier itself. The foreword was overtly a political statement by the Prime Minister so it was his wording and his comments throughout," he said.

"I didn't see it as something that I would change. My memory of the time is that this was quite clearly something the Prime Minister wrote which was going out under his signature."

Sir John acknowledged, with hindsight, that it would have been better if the now infamous claim that Saddam had WMD which could be deployed within 45 minutes referred to battlefield munitions rather than ballistic missiles.

But he insisted it had never been the intention to mislead the public about Saddam's capabilities.

"There was absolutely no conscious intention to manipulate the language or to obfuscate or to create a misunderstanding as to what they might refer to," he said.

Opening the hearing, the inquiry chairman Sir John Chilcot said the questioning would deal solely with Sir John's time as JIC chairman, and that other intelligence matters would be dealt with in closed hearings.

Following the war, it was discovered that Iraq had been unable to rebuild its WMD programmes, which were supposed to be the justification for the invasion by Britain and the US.

However, Sir John said the dossier, which was published by Mr Blair in September 2002 - six months before the invasion - had been drawn up against a background of strengthening intelligence about Saddam's WMD capabilities.

He said at the start of the month the JIC had received what was described as "reliable and authoritative" new intelligence which led it to "firm up" its assessment that Iraq had both chemical and biological agents.

Sir John also described how two separate intelligence reports came in the final days before the war, casting doubt on whether Saddam could use chemical or biological weapons.

The first, which arrived on March 7 - 13 days before the invasion - said Iraq had no missiles which could reach Israel and none which could carry germ or biological weapons.

It added that the Iraqi leadership had ordered the dismantling of its Al Hussein ballistic missiles, in order to avoid detection, although they could be quickly reassembled.

The MoD's Defence Intelligence Staff noted that, while it was possible they could be reassembled in one or two days, it could take longer.

The further report then came in on March 17 saying Iraq's chemical weapons had been disassembled and dispersed and would be difficult to reassemble.

Sir John said the final intelligence was discussed by the JIC on March 19 - the eve of the invasion - and a report was issued which would have gone straight to the Prime Minister's office.

"I was certainly working absolutely on the basis that these updates were being read carefully," he said. "The intelligence reports went through to the Prime Minister and to senior ministers."

However, he said the reports did not represent a "game changing moment" as the assessment that Iraq had usable chemical and biological warfare capabilities remained unchanged.