The party's foreign affairs spokesman Michael Moore blamed the change on an "illegal" war in Iraq and a "legacy of neglect" in Afghanistan.

He said hard questions had to be asked about UK forces' role in Afghanistan amid the mounting casualties.

And he called for a new strategy in Iraq which he said was "on the brink of civil war".

In a scathing attack on the government's foreign policy, Mr Moore warned that global unity had been replaced by bitter political dispute.

"Where once there was a credible British foreign policy, now we are at odds with much of the world," he told the Brighton conference.

"Our armed forces must have the weaponry, the equipment and the assets they need. And our Nato allies must have a coherent strategy and provide the resources to make it work."

'Mess'

An urgent new strategy was needed in Iraq, which was "on the brink of civil war," he said, adding that must be based on reconciliation, "not indefinite detentions and the abuse of human rights".

He said: "Without a new strategy, the continuing presence of British troops must be called into question.

"The government took us into this mess. It must now prepare the ground to get us out of it."

Mr Moore said the last few years had been a "dismal period" in British foreign policy.

But this summer it "reached a new low" over the Middle East.

The prime minister's failure to call for an immediate ceasefire as the violence escalated in Lebanon left Britain "diminished" in the eyes of the world.