Tony Blair has said he was unaware the 45 minute claim over Iraq's WMD meant only battlefield weapons when he urged MPs to vote for war in March last year.
Mr Blair said evidence of weapons programmes were uncovered
His comments came during a Commons debate on the Hutton report as a former intelligence official said information may have been "misinterpreted".
The September 2002 dossier said Iraq could deploy chemical and biological weapons within 45 minutes.
The Hutton inquiry was told the claim referred only to battlefield weapons.
But Mr Blair stood by his decision to join the US in invading Iraq, and emphasised to MPs that the Hutton report had cleared the government of "sexing up" its Iraq dossier.
And he called the BBC report which sparked the Hutton inquiry "100% wrong".
Fears over WMD were a cornerstone of the government's case for war with Iraq.
But the prime minister said on Wednesday he had not known what sort of weapons were being referred to at the time of the Commons vote on 18 March 2003.
Joint Intelligence Committee chairman John Scarlett told the inquiry the intelligence about the threat posed by Saddam Hussein's forces referred only to weapons such as mortars and shells but not long-range ballistic missiles.
Defence Secretary Geoff Hoon said at the inquiry he had known the intelligence only referred to battlefield weapons but did nothing to correct media reports.
But former foreign secretary Robin Cook, who quit the government because of his opposition to the war, expressed surprise about the idea Mr Blair was unaware of the nature of the weapons referred to.
"In my resignation speech I did make the very point that we were considering battlefield weapons and that Saddam probably had no real weapons of mass destruction," he said.
"I find it difficult to reconcile what I knew and what I am sure the prime minister knew at the time we had the vote in March."
Tory foreign affairs spokesman Michael Ancram said later Mr Blair's response raised "serious questions about what the government knew when Britain went to war with Iraq".
The House of Commons debate was briefly disrupted when protesters heckled Mr Blair prompting Speaker Michael Martin to suspend the sitting while the public gallery was cleared.
In the chamber, Mr Blair dismissed fresh concern about the intelligence gathered about Iraq and again defended his decision to go to war.
He told MPs he accepted the Iraq Survey Group had not found the banned weapons he had expected to be uncovered, but they had found evidence of weapons programmes.
Even if the group found nothing more "we would have been irresponsible in the highest degree not to have acted against Saddam", he argued.
But Dr Brian Jones, a retired senior official in the Defence Intelligence Staff (DIS), told the Independent newspaper the DIS' "unified view" was for there to be careful caveats about assessments of Iraq's chemical and biological weapons.
But they had been overruled by the heads of the intelligence agencies.
Mr Blair said Dr Jones' concerns had been considered by the head of defence intelligence, who decided the dossier's wording was correct.
Liberal Democrat leader Charles Kennedy complained a new inquiry into intelligence chaired by ex-cabinet secretary Lord Butler would not address the "fundamental question which the public want addressed", which was the political judgment to go to war.