After "searching his conscience" Tony Blair has said he still believes the Iraq war was justified.

The prime minister's comments came after criticism of his handling of intelligence in the run up to the Iraq war.

A report by former Cabinet secretary Lord Butler expressed concern at the way in which the prime minister leads his government.

His study concluded that procedures may not be less effective now than under previous administrations.

"However, we are concerned that the informality and circumscribed character of the government's procedures which we saw in the context of policy-making towards Iraq risks reducing the scope for informed collective political judgement," said the report.

It added that such risks were "particularly significant" in areas such as the use of intelligence on weapons of mass destruction.

But Blair pointed to the findings that no one had deliberately attempted to mislead the country.

"No one lied, no one made up the intelligence, no one inserted things into the dossier against the advice of the intelligence services," he told MPs.

"Everyone genuinely tried to do their best in good faith for the country in circumstances of acute difficulty.

"That issue of good faith should not be at an end."

War justified

The prime minister said there was another key issue relating to the failure to discover any weapons of mass destruction.

"We expected and I expected to find actual usable chemical or biological weapons shortly after we entered Iraq," Blair admitted.

"I have to accept as the months have passed it seems increasingly clear that at the time of invasion Saddam did not have a stockpile of chemical or biological weapons ready to deploy."

But he went on to counsel against concluding that the war was unjustified.

"I have searched my conscience not in a spirit of obstinacy but in genuine reconsideration in the light of what we now know in answer to that question," he said.

"And my answer would be this: that the evidence of Saddam's weapons of mass destruction was indeed less certain, less well founded than was stated at the time.

"But I cannot go from there to the opposite extreme."

Blair insisted that the former Iraqi leader "had no intention of ever cooperating fully with the inspectors".

"Had we backed down in respect of Saddam, we would never have taken the stand we needed to take on weapons of mass destruction," said the prime minister.

"For any mistakes made, as this report finds, in good faith I of course take responsibility. But I cannot honestly say I believe getting rid of Saddam was a mistake at all.

"Iraq, the region and the wider world is a better and a safer place now."

'Credibility'

In his response, Michael Howard said the prime minister had misled the country and misrepresented intelligence findings.

He quoted Joint Intelligence Committee reports to Downing Street pointing to "sporadic" and "patchy" information on Iraq and contrasted them with much firmer statements from Blair.

The Conservative leader said the "key questions" were whether "the intelligence given to the prime minister was accurate and did the prime minister give an accurate representation of it to the country".

The intelligence services' "qualified caveats became his unqualified certainties" the Commons was told.

Howard fell short of calling for Blair to resign but said the prime minister's admission of culpability was not enough.

"It is not a question of responsibility it is a question of credibility," he said.

"The question he must ask himself is does he have any credibility left?"

The Liberal Democrats declined to participate in the Butler inquiry, saying it should have considered the political decision to go to war.

And party leader Charles Kennedy said the full advice on the legality of the war should be made public given the failure of the intelligence on Iraq.

He added that the report showed that UN inspections had been successful in destroying Iraq's weapons of mass destruction.

Kennedy concluded by calling for a further inquiry into the causes of the war, as Lord Butler's committee had "not been able to address the fundamental question that many have wanted addressed from start to finish".