Here are some of the key statements made by the prime minister about Saddam Hussein's weapons - before and after the war.
10 April 2002, House of Commons
"Saddam Hussein's regime is despicable, he is developing weapons of mass destruction, and we cannot leave him doing so unchecked.
"He is a threat to his own people and to the region and, if allowed to develop these weapons, a threat to us also."
24 September 2002, House of Commons
"It [the intelligence service] concludes that Iraq has chemical and biological weapons, that Saddam has continued to produce them, that he has existing and active military plans for the use of chemical and biological weapons, which could be activated within 45 minutes, including against his own Shia population; and that he is actively trying to acquire nuclear weapons capability..."
25 February 2003, House of Commons
"The intelligence is clear: (Saddam) continues to believe his WMD programme is essential both for internal repression and for external aggression.
"The biological agents we believe Iraq can produce include anthrax, botulinum, toxin, aflatoxin and ricin. All eventually result in excruciatingly painful death."
11 March 2003, MTV debate
"If we don't act now, then we will go back to what has happened before and then of course the whole thing begins again and he carries on developing these weapons and these are dangerous weapons, particularly if they fall into the hands of terrorists who we know want to use these weapons if they can get them."
18 March 2003, House of Commons
"We are asked now seriously to accept that in the last few years-contrary to all history, contrary to all intelligence-Saddam decided unilaterally to destroy those weapons. I say that such a claim is palpably absurd."
4 June 2003, House of Commons
"There are literally thousands of sites. As I was told in Iraq, information is coming in the entire time, but it is only now that the Iraq survey group has been put together that a dedicated team of people, which includes former UN inspectors, scientists and experts, will be able to go in and do the job properly.
"As I have said throughout, I have no doubt that they will find the clearest possible evidence of Saddam's weapons of mass destruction."
8 July 2003, Evidence to Commons liaison committee
"I don't concede it at all that the intelligence at the time was wrong.
"I have absolutely no doubt at all that we will find evidence of weapons of
mass destruction programmes."
16 December 2003, Interview with British Forces Broadcasting Service
"The Iraq Survey Group has already found massive evidence of a huge system of clandestine laboratories, workings by scientists, plans to develop long range ballistic missiles."
16 December 2003, Interview with BBC Arabic Service
"I don't think it's surprising we will have to look for them. I'm confident that when the Iraq Survey Group has done its work we will find what's happened to those weapons because he had them."
4 January, 2004, Speech to British forces near Basra, Iraq
"Repressive states are developing weapons that could cause destruction on a massive scale."
11 January 2004 , Interview with BBC Breakfast with Frost
What you can say is that we received that intelligence about Saddam's programmes and about his weapons that we acted on that, it's the case throughout the whole of the conflict.
I remember having conversations with the chief of defence staff and other people were saying well, we think we might have potential WMD find here or there.
Now these things didn't actually come to anything in the end, but I don't know is the answer. And what I do know is that the group of people that are in there now, this Iraq survey group, they produced an interim report."
25 January 2004, Interview with the Observer newspaper
"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."
3 February, 2004, evidence to Commons liaison committee
"What is true about (ex-Iraq Survey Group head) David Kay's evidence, and this is something I have to accept, and is one of the reasons why I think we now need a new inquiry - it is true David Kay is saying we have not found large stockpiles of actual weapons."
6 June, 2004, BBC Radio 4 Today programme
"What we also know is we haven't found them [weapons of mass destruction] in Iraq - now let the survey group complete its work and give us the report... They will not report that there was no threat from Saddam, I don't believe."
6 July, 2004, evidence to Commons Liaison Committee
"I have to accept we haven't found them (WMD) and we may never find them, We don't know what has happened to them.
"They could have been removed. They could have been hidden. They could have been destroyed."
14 July, 2004, statement on the Butler report
"We expected, I expected to find actual usable, chemical or biological weapons after
we entered Iraq.
"But I have to accept, as the months have passed, it seems increasingly clear
that at the time of invasion, Saddam did not have stockpiles of chemical or
biological weapons ready to deploy."
28 September, 2004, keynote Labour conference speeech
"The evidence about Saddam having actual biological and chemical weapons, as opposed to the capability to develop them, has turned out to be wrong. I acknowledge that and accept it. I simply point out, such evidence was agreed by the whole international community, not least because Saddam had used such weapons against his own people and neighbouring countries.
"And the problem is, I can apologise for the information that turned out to be wrong, but I can't, sincerely at least, apologise for removing Saddam.
"The world is a better place with Saddam in prison not in power."
"I can apologise for the information being wrong but I can never apologise, sincerely at least, for removing Saddam. The world is a better place with Saddam in prison."
29 September speaking on BBC Radio 4's Today programme
The prime minister was asked about UN secretary general Kofi Annan's assertion that the war with Iraq was illegal.
"That is his view - it is not our view," Mr Blair said.
"The view we took at the time and we take it now is that the war was justified legally because he [Saddam Hussein] remained in breach of UN resolutions."