The Tories have called it "appalling" that ministers did not try to "put the record straight" over the now infamous 45 minute claim about Iraq's weapons.
The 45-minute claim was in the September 2002 dossier
Shadow Foreign Secretary William Hague said the claim, in a government dossier, appeared to have been privately "discounted" long before war.
Foreign Secretary Margaret Beckett had earlier said the 45 minute claim was of "little relevance" and used only once.
"Perhaps people began to quickly think 'I'm not sure about that'," she said.
The claim - that weapons of mass destruction could be used within 45 minutes of Saddam Hussein giving the order to do so - was "never used once" in Commons debates, she added .
She insisted that there had been no "deceit" on the part of the Prime Minister Tony Blair in the build-up to war with Iraq in 2003.
'Intention and desire'
Mrs Beckett told BBC Radio 4's Today: "What was said throughout was that Saddam Hussein was a threat to his region and that he had the intention and the desire to be a threat much more widely than his immediate region."
The 45-minute claim was included in the body and Tony Blair's foreword to the September 2002 dossier on Iraq's Weapons of Mass Destruction. It subsequently became the front page headline in a number of newspapers.
It became infamous after a BBC report suggested in May 2003 that it had been inserted into the dossier against the wishes of the intelligence services, as Number 10 sought to "sex up" the case for war.
That BBC report prompted a row between the government and the BBC, which ended with the death of the source for the story, government WMD expert Dr David Kelly.
His death was then investigated by the Hutton inquiry, which concluded that he had committed suicide and that the 45 minute claim was in the dossier with the full blessing of the then chairman of the Joint Intelligence Committee, John Scarlett, who is now head of MI6.
Mrs Beckett, asked about the 45-minute claim on the Today programme, said it "was a statement that was made once and was thought to be of such little relevance, and perhaps people began to quickly think 'I'm not sure about that'.
"It was never used once in all the debates or questions in the House of Commons."
Mrs Beckett also said: "Nobody thought it was relevant. Nobody thought it was actually a big sweeping statement."
Asked whether it had seemed Saddam posed a direct threat to the UK, she said: "No one put that argument.
"What we put was that argument that he was a threat to that region and that he had the ambition to be a threat to the wider world.
"Britain does have interests outside just our own shores."
But Mr Hague said: "If it is true that the 45-minute claim had been discounted before the invasion, it is appalling that there seems to have been no effort or coordination between ministers to put the record straight.
"This is yet another reason to dismantle Tony Blair's sofa policy-making and restore Cabinet government."
The comments come after it was revealed last week that former UK diplomat Carne Ross had told the 2004 Butler review into Iraq intelligence that "at no time did HMG (Her Majesty's Government) assess that Iraq's WMD (weapons of mass destruction) posed a threat to the UK or its interests".
He also claimed that there was no evidence of "significant holdings" of chemical or biological weapons in the possession of Saddam prior to the invasion.
"There was, moreover, no intelligence or assessment during my time in the job that Iraq had any intention to launch an attack against its neighbours or the UK or the US," he added.
Mr Ross's evidence has only just been published because of initial fears it breached the Official Secrets Act.
Mrs Beckett said: "I don't find what Mr Ross says particularly surprising and I certainly don't find it shows deceit."
The 45 minute claim was officially withdrawn two years after the dossier's publication.