Mr Cook's remarks came as European Union leaders meet in Brussels to debate a German plan offering a 24-hour lull in air strikes if the Yugoslav President Slobodan Milosevic starts withdrawing his forces from Kosovo.

In a speech at the Lord Mayor of London's Easter Banquet, Mr Cook said standing by while Serbian forces engaged in violent ethnic cleansing would have seen fascism re-born in Europe for the first time since World War Two.

'Never again'

Mr Cook said: "In 1945 we surveyed what we found in Europe - the death camps, the indecent bureaucracy of the extermination programme, the pathetic survivors and the millions of victims and we said never again.

"It was a pledge on which the modern Europe was built. It is a pledge we must redeem in Kosovo."

Robin Cook: Crimes of the past must not be repeated

He continued saying: "In the past two weeks we have borne witness to forced movements by train, to thousands starving in squalid camps, to pathetic masses shorn of their homes and their papers for no other reason than their ethnic identity.

"These are the sights we said we would banish from our continent forever."

He added: "Had we done nothing, we would have been complicit in that evil.

"Had we done nothing, we would have betrayed the modern Europe we are trying to build."

The foreign secretary also re-stated Nato's terms for the end to the air strikes.