Robin Cook: "The International War Crimes Tribunal must be allowed to carry out an investigation"

In a statement in the House of Commons, Mr Cook described to MPs the sight of the massacre at Racak - widely believed to have been carried out by members of the Serb security forces.

Robin Cook met with George Robertson and the prime minister to discuss Kosovo

The victims of the massacre, some of whom included "grey-haired old men", had been shot in the head and neck, Mr Cook said.

The foreign secretary told MPs: "It is simply not credible those who were killed were casualties of military conflict."

He said he was repelled by the cold and calculated method of this massacre.

"In every understanding of the term, this was a war crime," Mr Cook said.

Britain would demand through the UN Security Council that the international War Crimes Tribunal was given access to Kosovo to investigate the killings, the foreign secretary said.

If peace and civility are to be established in Kosovo it is vital to escape the endless cycle of atrocity, he added.

Serbian President Slobodan Milosevic must be clear that the threat of Nato military action last autumn was "only suspended because of his agreements to cease fire, to withdraw part of his military units in Kosovo and to return the rest to barracks".

Neither side, the Serbs or the Kosovo Liberation Army, could win this war, said Mr Cook.

"I urge both sides now to get down to meaningful negotiations," he said.

It was the only way to prevent such atrocities for occurring, he added.

Mr Cook warned all those who had contributed to the "political stalemate" must bear their share of responsibility for creating the atmosphere in which the ceasefire had crumbled.

He expressed deep regret meaningful talks on the detailed paper drawn up three months ago by US and EU special representatives on the way forward had not yet begun.

Shadow Foreign Secretary Michael Howard said it had been impossible to see the scenes of the massacre on television without being deeply moved or deeply angered.

He asked Mr Cook where things stood on the possibility of Nato air strikes.

The foreign secretary replied it would take a political decision by the North Atlantic Council to trigger any military action.

"The planes remain on 96 hours' notice," he told Mr Howard.

But he warned that bombing Serbian installations was not the right way to bring the individuals responsible for the massacre to justice.

General Wesley Clark: Nato has sent him to have talks with the Yugoslav government

Before making his statement to the House on Monday, the foreign secretary and Defence Secretary George Robertson met with Prime Minister Tony Blair to discuss the crisis.

Nato has sent its two top generals, Wesley Clark of the US and the German head of its military committee Klaus Naumann, to Belgrade to hold talks with the Yugoslav government.

Liberal Democrat leader Paddy Ashdown, who has visited the region a number of times recently, said not only should President Milosevic be forced to allow UN investigators visas - which he has denied up to now - but Nato should make clear its willingness to use force to protect Albanian villages.

Earlier, Mr Ashdown said there was now a question mark over the "moral authority" of Belgrade to govern Kosovo, which meant Nato could reconsider the whole position of the province in relation to Serbia and Yugoslavia.