Ex-cabinet ministers Robin Cook and Clare Short have attacked Tony Blair's stance over Iraq's alleged weapons of mass destruction.
Robin Cook: Governments should never cover up their mistakes
Mr Cook told the BBC the government had made a "monumental blunder" on the issue and called for an independent inquiry.
And Ms Short said the prime minister had duped the public by putting political spin on weapons intelligence information, to justify the case for war.
But in an interview with Sky News, Mr Blair said he had "no doubt whatsoever" that Saddam Hussein had had nuclear, chemical or biological weapons, and said he would in due course produce that evidence.
Because all this was done secretly, the preparations for
post-conflict were poor
Former cabinet minister Clare Short
Former Foreign Secretary Robin Cook told BBC Radio 4's World This Weekend: "In the real world, governments make mistakes, but what they must never do is try to deny and cover up these mistakes."
Mr Cook said the UN weapons inspectors must return to Iraq to establish that Saddam did not have the capacity for weapons of mass destruction which would justify an invasion.
Mr Cook - who resigned as leader of the Commons over the war - said the notion of Saddam using any weapons of mass destruction within 45 minutes was wrong.
'Within 45 minutes'
"We have not found any of these chemical shells capable of being used in 45 minutes or 45 hours.
"We have been in Iraq, since the war ended, for over 45 days and we have not found a single chemical shell. It is obvious that that statement
Ms Short, who resigned as international development secretary in the aftermath of the war, said she believed Mr Blair had secretly agreed the date for war with US President George Bush last September.
She accepted Iraqi scientists had been trying to develop chemical and weapons.
But she also hit out at the government's claim that some of those weapons could be launched "within 45 minutes" of an order.
That "duped" people into thinking the threat was much more urgent when the reality was that there was time to do things properly, she argued.
"The claim the stuff was weaponised and might be used in 45 minutes was part of the secret commitment to a date, which meant everything had to be hurried along," she told BBC One's Politics Show.
There had been deceit too in the way France had been "vilified" as an excuse not to get a fresh UN resolution before the war, Ms Short added.
Earlier, Mr Blair, who is now in France for the G8 summit, said the results of interviews with Iraqi scientists and others had left him in no doubt on the weapons issue.
There were also investigations under way at "hundreds" of Iraq sites which were turning up more evidence, he said.
Mr Blair said: "Over the coming weeks and months we will
assemble this evidence and then we will give it to people.
Bitter divisions remain over Iraq
"And I have no doubt whatever that the evidence of Iraqi weapons of mass
destruction will be there. Absolutely," he said.
"Those people who are sitting there saying: 'Oh, it's all going
to be proved to be a great big fib got out by the security services, there will be no weapons of mass destruction' - just wait, and have
a little patience."
Meanwhile, the Conservatives are giving "serious consideration" over whether to call for an independent inquiry into the government's claims over weapons of mass destruction.
Michael Howard, the shadow chancellor, told BBC Radio 4's Westminster Hour: "If... the government engaged in deception in order to gain public support or get the support of the Labour Party for this war, that would be an immensely serious matter going to the heart of the integrity of our government."