Tony Blair has said he "has absolutely no doubt" the intelligence about weapons of mass destruction he received in the run-up to the Iraq war was genuine.
Mr Blair: I believed the intelligence we had at the time
And Downing Street says he is standing by his comments to the Observer newspaper, made before the head of the Iraq Survey Group resigned voicing scepticism about WMD.
The prime minister would not say whether he thought actual weapons will be found.
Mr Blair faces a testing week with the Hutton report and the top-up fees vote.
Ex-junior defence minister Lewis Moonie said it now looked likely the intelligence was "deficient".
In the interview with the Observer, Mr Blair said he still intended to be prime minister next Friday and his job was always "at risk".
He would not state whether he thought actual weapons would be found, saying it was a matter for the Iraqi Survey Group.
However he insisted: "I have absolutely no doubt in my mind that the intelligence was genuine.
"It is absurd to say in respect of any intelligence that it is infallible, but if you ask me what I believe, I believe the intelligence was correct, and I think in the end we will have an explanation."
On the day of the interview, US WMD search official David Kay resigned saying he did not believe Iraq possessed large stockpiles of chemical or biological weapons.
And at the weekend US Secretary of State Colin Powell conceded Iraq may not have possessed any WMD stocks before the war last year.
On Sunday a Number 10 spokesman said the prime minister's views had not changed.
Meanwhile Mr Moonie, a junior defence minister during the Iraq War who lost his post in June, said it was "increasingly looking likely" the pre-war intelligence was deficient.
He told Scottish Television: "Sooner or later we may well have to say 'yep, the intelligence was faulty and the decisions we took were based on the best evidence available, and the best evidence available wasn't good enough'."
But Dr Moonie insisted Mr Blair had "acted in good faith" when he argued the case for war.
The decision to go to war is under scrutiny from all sides
Environment Secretary Margaret Beckett said the evidence may be a "paper trail" of documents about weapons programmes rather than physical proof.
She told BBC Radio 4's The World This Weekend "every intelligence service in the world" believed Saddam Hussein had access to WMD and was prepared to use them.
But Liberal Democrat leader Charles Kennedy said Mr Blair's judgement on WMD was in question.
He told BBC One's Breakfast with Frost programme: "The more that we see the absence of weapons of mass destruction, the more we see both the prime minister and the President of the United States qualify what it is that the Iraq Survey Group may or may not uncover."
Meanwhile the Sunday Telegraph said Mr Blair would escape personal criticism from Lord Hutton over events which led to the death of arms expert Dr David Kelly.
Downing Street has refused to comment on the paper's suggestion the PM's aides have indicated he has not received a letter from Lord Hutton warning him he will be criticised when the report is released on Wednesday.
Conservative leader Michael Howard has written to Lord Hutton to ask for a list of unpublished submissions to his inquiry ahead of Wednesday's report.
The government, BBC, Andrew Gilligan and the Kelly family all made written submissions after the hearings ended.
Dr Kelly apparently committed suicide after being named as the suspected source for a BBC story on claims Downing Street "sexed up" the government's Iraq weapons dossier.