MPs warned the Prime Minister that bombing may not bring President Milosevic back to the negotiating table and could lead to a full-blown war with Serbia.
But, in a sombre statement, Mr Blair said that while the potential consequences of military action were serious, "the consequences of not acting are more serious still for human life and for peace in the long-term".
He added: "We must act to save thousands of innocent men, women, and children from humanitarian catastrophe, from death, barbarism and ethnic cleansing by a brutal dictatorship, to save the stability of the Balkan region, where we know chaos can engulf all of Europe." He said if Kosovo was left to the mercy of Serbian repression, there was "not merely a risk but a probability of re-igniting unrest in Albania, destabilising Macedonia and almost certain knock-on effects in Bosnia and further tension between Greece and Turkey. We cannot contemplate, on the doorstep of the EU, disintegration into chaos and disorder."
William Hague warned the Prime Minister that his party would not be willing to back the use of ground forces to fight for a peace settlement.
Action should have been taken sooner against the Serbs, rather than the issuing of a "string of last warnings and ultimatums ... the credibility of Nato has been called into question," the Tory leader added.
Menzies Campbell, for the Liberal Democrats, told Mr Blair: "The political aim should be to require the Milosevic government to pay such a high price in military assets that it is persuaded, even compelled to return to the conference table?"
Sir Peter Tapsell, the Tory MP for Louth and Horncastle, accused Mr Blair for using "weasel words" with the British people because air strikes alone would not achieve the Nato objectives.
"What the Government is proposing now is to make war on Serbia and it is a profound political mistake to suppose that Milosevic is not supported by the mass of the Serbian patriotic people, one of the great fighting people of Europe.
"The British people should be told now that we are embarking inevitably in ground operations that will result in heavy casualties."
But Clive Soley, the chairman of the parliamentary Labour Party, told Mr Blair that the British people had learned "more than anyone else that appeasement does not work". The British people would not allow anyone to forgive and forget the "barbaric crimes" which had been perpetrated in Kosovo, he added.
Tony Benn, the MP for Chesterfield, said Britain and its allies were "breaking international law", and attacked the Prime Minister for not holding a debate in the House of Commons on the issue.
David Winnick, the Labour MP for Walsall North, said: "When we listen to the voices of non-intervention, isn't it the case that those who argued for non-intervention were wrong about the Falklands in 1982, wrong about Kuwait in 1991, and certainly wrong about the help of the international community in bringing about a settlement in Bosnia in 1995, so why on earth should we believe they are right now?"