"The intelligence really left little doubt about Saddam Hussein and weapons of mass destruction," a defiant Tony Blair told parliament at the start of a debate into the inquiry.
The information "made it absolutely clear that we were entirely entitled on the basis of that to go back to the United Nations and say there was a continuous threat from (Iraqi leader) Saddam Hussein," he said.
An inquiry team led by former top civil servant Lord Robin Butler said last Wednesday much of the intelligence on Iraq's weaponry had later proved to be unreliable.
The report cleared Blair of any deliberate wrongdoing, but he has since come under pressure from opponents to explain how he interpreted the intelligence as showing Baghdad posed an immediate threat to the West, Blair's argument for backing the US-led conflict.
Conservative Party leader Michael Howard said there was an alarming gap between intelligence that was "sporadic, patchy, little and limited", and Blair's prewar statements that said it was "extensive detailed and authoritative".
"The prime minister once said that he was a pretty straight guy. But he has not been straight with the British people today. Why is it that for this prime minister 'sorry' seems to be the hardest word?" Howard said.
But Blair insisted Saddam Hussein's intentions had been completely clear, irrespective of whether or not any actual weapons of mass destruction (WMDs) were found after the fall of Baghdad.
"The prime minister once said that he was a pretty straight guy. But he has not been straight with the British people today. Why is it that for this prime minister 'sorry' seems to be the hardest word?"
Conservative Party leader
"It was absolutely clear that he (Saddam) had every intention to carry on developing these weapons, that he was procuring materials to do so and that, for example in respect of ballistic missiles, he was going way beyond what was permitted by the United Nations," Blair said.
The prime minister also vehemently defended his decision to go to war, saying Britain had entered into it "with a clear conscience and a strong heart".
"Removing Saddam was not a war crime, it was an act of liberation for the Iraqi people," he said to cheers from members of his ruling Labour Party.
However Blair also announced he would make some changes to the way the government dealt with intelligence after criticisms in the Butler report.
"The intelligence really left little doubt about Saddam Hussein and weapons of mass destruction"
British prime minister
The Joint Intelligence Committee, which co-ordinates intelligence efforts, would not be used to draw up any future dossiers setting out the case for a war, while all further documents would also include any caveats expressed by intelligence sources, he announced.
This was in response to a British government dossier on Iraq's WMDs issued by the government in September 2002 which has been at the centre of allegations when Blair and his ministers intensively promoted the case for war.