Speaking after efforts by Russian leaders to secure an end to the bombing produced movement from the Serbs, Foreign Secretary Robin Cook said that Mr Milosevic's proposals fell far short of what Nato wanted to see.

In a statement issued by Yugoslav state television, Mr Milosevic said he was ready to withdraw some forces from war-torn Kosovo if Nato halts air strikes.

Defence Secretary George Robertson: "This offer is not serious"

Defence Secretary George Robertson, speaking as his department confirmed that Harriers involved in Tuesday's raids had returned safely, called the proposal neither "a sensible nor a serious offer".

"He is not saying he'll stop the killing," he told BBC News. "He is not saying he will bring to troops back to where they were last October.

"I think it is indication that what is involved here is a bit of game - Milosevic making what looks like an offer on the face of it but which does not involve a cease-fire."

PM backs Schröder

Tony Blair's official spokesman said that the Prime Minister backed German Chancellor Gerhard Schröder.

"There is no question of halting the air strikes while Milosevic's forces are still out there carrying out their heaviest programme of ethnic cleansing," he said.

Allies throughout Nato have also dismissed the offer, including the US and Germany.

Hague attack

The UK is leading international efforts to aid refugees and an RAF plane carrying 42 tonnes of blankets and other supplies left for the region on Tuesday.

Hague: "Too little, too late"

But putting fresh pressure on the cross-party support for the Nato action, Conservative leader William Hague accused the Government of doing "too little too late" to help the refugees.

In a statement, Mr Hague said: "Whole villages have been uprooted, families with young children find themselves thrown out on to exposed roads, and elderly people are facing night after night out in the cold.

"Nato must have foreseen this kind of reaction by Milosevic to their present military action and must have made contingency plans.

Peter Hunt reports on the refugee aid programme

"However, I find it disturbing to read reports that the Government and its allies have made little or no preparations to deal with the human tidal wave now on the move in the Balkans.

"The aid package announced by Tony Blair yesterday is welcome, but it is too little too late.

"Nato needs to do much more."

He called on the government to set up refugee camps along the border, and provide emergency food, shelter, clothing and health care.

A high-level task force should be established to deal with the crisis, he said, to include representatives from charities and aid agencies already in the region.

Cross-party agreement has alrady been under strain after the leader of the Scottish Nationalists, Alex Salmond, attacked the morality of the air strikes.

Welsh nationalists Plaid Cymru have also expressed strong doubts over the campaign.

London protest

On Tuesday evening Labour MP Tony Benn spoke out against the Nato action as 500 protesters gathered for a heated public meeting in London.

Mr Benn, who has repeatedly spoken out against the bombing of the Serbs, was surrounded by supporters at the Friends Meeting House in Euston.

"I am quite clear that the bombing must stop and the power of negotiation must be taken away from Nato and given to the United Nations," he said.