In a statement in the House of Commons, Tony Blair said such an interpretation was "simply absurd".

The "ethnic cleansing" being perpetrated in Kosovo resulted from long-planned manoeuvres by Serbian President Slobodan Milosevic.

Mr Blair told MPs: "Even as we speak there are continuing atrocities perpetrated by Milosevic against his civilians.

"The massacres we are witnessing now were planned by Milosevic over the past two months.

"It is now clear Serb participation in the French talks was a cover for preparations for war.

"For every act of barbarity, every slaughter of the innocents, Milosevic should be made to pay a higher and higher price."

Opposition support

The prime minister said the UK was taking steps to help refugees who had fled Kosovo during the bombing.

But reports of increasing human rights abuses could not lead to the end of Nato's offensive, he said.

"Our response, far from slowing down or halting the allied action, must be to intensify it and see it through to its conclusion."

Conservative leader William Hague gave the prime minister his backing.

"Nothing would be more disastrous for the humanitarian situation or the credibility of Nato than if we backed out of what has been started."

'Intensify campaign'

In a BBC interview, Mr Blair said about 20,000 people had been driven from their homes in the two days before bombing began. Reports suggest a fifth of the population have fled since Nato action began.

Mr Blair said: "We must make Milosevic pay a very heavy price for what he's doing.

Robin Cook and Tony Blair are defending the offensive

"No-one thought that the Nato campaign would make him stop simply after a few days. This is a dictator that's built up his position over a long period of time.

"I think that the Nato campaign has to intensify, targeted on the military capability that Milosevic is using to carry out these acts of barbarity in Kosovo, and we have to carry it on and see it through.

"Because the alternative is to have a situation where Kosovo is subject to ethnic cleansing, where thousands of people, wholly innocent people, are killed, and where the whole of that region becomes destabilised again."

'Ethnic cleansing'

In a briefing, the UK foreign secretary detailed "atrocities" being carried out by Serb forces in Kosovo.

Robin Cook named the leaders behind Serbian "ethnic cleansing" and promised he would make sure they were brought to justice.

The BBC's George Eykyn: "Mr Cook said a new apartheid was being created in Europe"

Mr Cook said he had received fresh reports of executions and people being rounded into camps.

More than a year had passed since the world first saw pictures of massacres perpetrated in Kosovo, the foreign secretary said.

Such images had kept coming until Belgrade expelled all foreign news crews from the region when Nato bombing started.

"We can only estimate and guess at what is the purpose of the concentrating of these refugees," Mr Cook said.

"But we remember the way many refugees were concentrated and herded together and executed by Serbia in the Bosnian war."

Mr Cook said President Milosevic had long planned a spring offensive and the violence on the ground in Kosovo would have occurred irrespective of Nato's offensive.

"This is ethnic cleansing of exactly the kind we saw in Bosnia," he said.

"One of the great achievements in the modern age has been to see the end of apartheid in Africa. We have not celebrated the end of apartheid in Africa to see it resurrected in Europe."

RAF Harriers successful

The Ministry of Defence revealed RAF Harriers successfully blew up a munitions dump used by Serbian military police on Sunday night.

Chief of Defence Staff General Sir Charles Guthrie said the aim of the fifth day of Allied bombing had been to target the Serbs' air defence system.