Tony Blair told the recalled Commons that the terrorist attacks on the US were "attacks on the basic democratic values in which we all believe so passionately and on the civilised world."
The attacks were "an act of wickedness for which there can be no justification," said Mr Blair. "These terrorists have made themselves the enemies of the entire civilised world."
He added: "We have been warned by the events of the eleventh of September and we should act on this warning."
Any response "must and will be based on hard evidence". Once the approppriate action had been decided on, it would be carried through in a determined manner.
The first priority would be bringing those responsible to justice: "Those that harbour or help them have a choice, either to cease their protection of our enemies or be treated as an enemy themselves."
He also sounded a calming note: "If as appears likely it is so-called Islamic fundamentalists, we know they do not speak or act for the vast majority of decent law-abiding Muslims throughout the world. I say to our Arab and Muslim friends neither you nor Islam is responsible for this."
Iain Duncan Smith, the new leader of the Opposition, said that as many as one in 10 of the New York victims could have been British citizens.
A service was being held at St Paul's Cathedral today as a mark of respect for the thousands who died in Tuesday's attacks in New York and Washington.
The Dean of St Pauls, John Moses, said: "This an opportunity for people in the UK to stand shoulder to shoulder with the American people...and in a very small way share their grief over this tragedy and join together in prayer."Reuse content