In a sombre statement to the Commons, Tony Blair denied it was a "specific objective" to remove the dictator, stressing that such action would require hundreds of thousands of ground troops.
"The decision to take military action against Iraq was taken with great regret. It is a heavy responsibility. There will be casualties in Iraq, despite all our efforts. We have absolutely no quarrel with the Iraqi people but we have acted because we have to counter a real and present danger from a tyrant who has never hesitated to use whatever weapons come to hand."
Rising to a crowded chamber, Mr Blair strongly refuted the timing of the air strikes were "somehow linked to the internal affairs of the United States", saying: "I have no doubt whatsoever that action is justified now. That is my strongly personal view."
Had Bill Clinton acted differently, out of regard to internal matters to United States politics, that would have been a dereliction of his duty as President, he added.
The Prime Minister said that once the military action was over, the UN would be better placed than if it had to go on dealing with a Saddam Hussein whose military capability had not been weakened.
"First reports from last night's operations suggest that they were successful and inflicted the kind of military damage we were seeking.
"If Saddam will not see reason, then after this military operation is concluded, we will work to ensure that Saddam's weakened military capability cannot be rebuilt and that the threat he poses is fully contained. We have the ability to do so, even without Unscom [the UN weapons inspection commission] if necessary."
Britain would "maintain and enforce" rigorously the existing sanctions, Mr Blair said. "If necessary, and if we have serious evidence from our intensive surveillance, or from our intelligence, that his capability is being rebuilt, we will be ready to take further military action. Saddam should have no doubt of our continuing resolve."
But Mr Blair said the objectives of "degrading" Saddam Hussein's ability to build weapons of mass destruction and weakening his military capability were "achievable".
The action taken was "proportionate to the serious dangers he poses to his immediate neighbours, the Middle East region and the international community more widely.
"The targets, throughout Iraq, have been very carefully selected to reflect these objectives. We are taking every possible care to avoid civilian casualties or damage to ordinary civilian infrastructure."
Mr Blair told MPs it was "vital that people understand that the threat from Saddam Hussein was real, not theoretical" because the UN weapons inspectors had been "constantly harassed, threatened, deceived and lied to".
They had "achieved a huge amount" in destroying Iraq's chemical and biological weapons capability but "much - too much - remains unaccounted for".
The Prime Minister praised the bravery and professionalism of the allied forces, saying: "I know the whole House will join me in wishing them as well as they risk their lives to help ensure peace and stability in the Middle East and more widely."
To cheers from all sides, he added: "We are proud of them."
Later, during further debate on the air strikes, Robin Cook, the Foreign Secretary, said: "As long as Saddam remains in power, we will remain resolute in our determination that he will not be allowed to fulfil his ambitions to develop weapons of mass destruction."
The Tory leader, William Hague, offered "full support" for the action, pledging: "We on this side of the House share your view that you and President Clinton had no alternative but to order a military response to the continuous deceit of Saddam."
George Galloway, Labour MP for Glasgow Kelvin, was jeered by his own party when he said Britain was "diminished and degraded" by its attacks on Iraq.
He told the Prime Minister: "I wonder if you thought, as I did at lunchtime, as the bleeding women and children were carried into hospitals that those who were diminished and degraded were not the Iraqis, but us - diminished and degraded by being reduced to being a tail on this verminous and mangy Desert Fox."
"The attack has not been led by Richard the Lionheart, but by Clinton the Liar," he added.
Dennis Canavan, Labour MP for Falkirk, added: "British and Iraqi lives are being put at risk in a desperate attempt to save Clinton's skin."
Menzies Campbell, Liberal Democrat foreign affairs and defence spokesman, said these were "sombre and anxious moments" for Britain. "The air strikes should be seen neither as a cause for celebration nor for satisfaction, but as a painful necessity and as a last resort to which we have been driven when all other options have been exhausted."
Stuart Bell, Labour MP for Middlesbrough, asked Mr Blair: "Will you recall how German troops were in the Rhineland in 1936? If Adolf Hitler had been stopped then, 20 million people may have not lost their lives."
Parliamentary Labour Party chairman Clive Soley, MP for Ealing Acton, gave the action his full backing, adding that many British Muslims opposed President Saddam.
He said: "Many of them would agree with me in saying that dictators that have so disfigured the face of the 20th century do need to be stopped. Let us go into the 21st century proud of the role that we have played, difficult though it may be."
However, Tony Benn, Labour MP for Chesterfield, condemned the attacks, maintaining the Government was breaking UN regulations because two members of the Security Council, Russia and China, opposed the air strikes.
"Military action was tried seven years ago when 200,000 Iraqis were killed, many of them quite innocent, and Saddam is stronger than he was.
"There are many people in the world - and I am one of them - who believe that what has been done yesterday is deeply immoral and contrary to an ethical foreign policy of which we boast."
Tam Dalyell, MP for Linlithgow, echoed his concerns, raising the threat of environmental damage if missiles hit military sites.
Gerald Kaufman, MP for Manchester Gorton, told MPs how there was a "feeling of nausea" among MPs at the suggestion that Mr Blair was doing a "cronyish favour" for Bill Clinton. He added: When our men are being asked to risk their lives that is despicable."
Bruce George, chairman of the Commons Defence Select Committee, said the present "charge" illustrated that "if we decide as a nation to spend less than currently projected for defence then we must be honest and say that there will be tasks like this that we are not going to be able to discharge".
Tory former cabinet minister, Douglas Hogg, MP for Sleaford and North Hykeham, said one tactic to oust Saddam Hussein would be to encourage an uprising by Shia Muslims in the south of Iraq and by the Kurds in the north.
But he warned that without "substantial and effective military cover" from the US and UK this should not be instigated because it could lead to a "great loss of life".Reuse content