An estimated 2,000 protestors marched from Victoria Embankment to Trafalgar Square.

They were followed by about 400 pro-Nato demonstrators, mainly from the Albanian community, who jeered and whistled from behind barriers at the entrance to The Mall.

Several backbench Labour MPs - including Tony Benn and Tam Dalyell - gave their support to the protest.

Tam Dalyell: "Bombing serves no purpose"

Mr Dalyell told the BBC that the bombing of Serb targets had only served to make President Slobodan Milosevic more popular with his people.

"Bombing serves no purpose. It is counterproductive," he said as crowds whistled and shouted slogans around him.

"Two years ago over 200,000 people had a demonstration far louder than this in Belgrade against Milosevic. Those same people last week demonstrated for him. Now public opinion is entrenched behind him. This is what bombing does."

Tam Dalyell: "Bombing is counterproductive"

The Committee for Peace in the Balkans hopes to draw in significant public support and force the government to pay attention to its opinions.

It believes the alliance's case for military action is "unpersuasive" and wants a solution found through mediation and negotiations.

The group is calling for strengthened peacekeeping measures "without escalation of the conflict by military intervention", while condemning all atrocities committed in the region.

War money 'should be spent on aid'

Veteran Labour MP Tony Benn outlined the views of many of the protesters.

"We are saying, stop the bombing now. And we are saying that all money and effort now devoted to war should be diverted to the enormous humanitarian problems that not only concern the people of Kosovo, but the people of Yugoslavia who are being bombed day after day after day," he said.

"And we want the UN to take back responsibility for finding a peaceful solution for the problems in the Balkans."

Earlier in the day he said any decision on action should have been made through the United Nations, not Nato. "What America and Britain is trying to do is take over Europe in the name of Nato," he said.

Protesters were jeered by pro-Nato demonstrators

Supporting the protest was campaigning journalist John Pilger. He said his profession was going through "a period of extraordinary shame".

"Unless decent public opinion is informed, and unless it is marshalled to stop the bombing, I believe that Serbia will suffer the kind of ferocity of attack that we won't know about," he said.

CND campaigner Bruce Kent paid tribute to the Serb people, calling them "incredibly brave" over the years and in their resistance to the Nazis during World War II.

"I am not speaking for this flag or that flag, I am speaking for human beings who are suffering."

'No u-turn' for Nato

As marchers protested along the Mall, Nato and the UK Ministry of Defence insisted the campaign would continue until President Milosevic backed down.

Robin Cook: "Nato is determined to achieve its objectives"

Foreign Secretary Robin Cook repeated the policy that there were no plans of preparations for a ground invasion of Kosovo, despite growing calls to do so. "There's no u-turn," he said.