Tony Blair yesterday mounted an uncompromising defence of his hardline stance on Iraq, despite growing unrest among Labour MPs at the prospect of war with Baghdad.

He warned it would be "absolutely disastrous" for world security if Saddam Hussein was not stripped of his weapons of mass destruction - and made it clear that, if necessary, Britain and the US would go it alone.

The Prime Minister used his monthly Downing Street Press conference for a stinging attack on critics of British involvement in possible military action, describing them as "naive and misguided".

Mr Blair expressed confidence that the United Nations Security Council would pass a fresh resolution specifically authorising military action if Iraq did not disarm voluntarily - a key concern for many Labour backbenchers.

However, he warned that opponents of military action within the UN must not be allowed to impose an "unreasonable or unilateral block" on the use of force.

"Don't be under any doubts whatever. If there is a breach of the UN resolution that we have passed, then action will follow,"said Mr Blair.

"When the UN has taken a stand on weapons of mass destruction, where they have said to Iraq you have to disarm yourself of these weapons, are people really saying that if there is a breach of that UN resolution that no action should follow?

"If we did that we would send a message to the outside world which would, in my view, be absolutely disastrous for the security of our world."

Despite the hardline rhetoric, Mr Blair again played down the importance of the report of chief UN weapons inspector Hans Blix, due to be presented to the Security Council on January 27.

While he acknowledged that January 27 was an "important day", he made clear that it was not a deadline for the completion of the inspection process.

"None of us are putting speculative or arbitrary timeframes on this," he said. "Let the inspectors do their task."

Although Dr Blix has said the inspectors had so far failed to come up with the "smoking gun" which proved Iraq still had weapons programmes, Mr Blair hinted he believed they would, at some point, find some clear evidence.

Mr Blair flatly rejected complaints that the issue was being driven entirely by the US, saying he had actually raised the subject at his first meeting with President Bush in February 2001.

"If George Bush and America were not raising this issue, I would be urging them to raise it," he said.

Mr Blair dismissed as "complete nonsense" claims that the Cabinet was split on the issue, despite International Development Secretary Clare Short's weekend warning that Britain had a "duty" to prevent a rush to war by the US.

However, Shadow Foreign Secretary Michael Ancram said last night: "While Tony Blair was relatively clear, his Cabinet colleagues are all over the place."

Former Labour defence minister and Newcastle North MP Doug Henderson told BBC Radio 4: "The public are very sceptical, certainly in my constituency."

He said people wanted to know the real reason for taking military action, adding: "Does it make us safer from terrorism or not?"