Future generations will be haunted by the consequences of weakness if the threat of Iraq's weapons is not confronted, Tony Blair has warned.

Mr Blair's defence of his Iraq policy in the House of Commons at prime minister's questions came shortly after a closed meeting at which he tried to win over doubters among his own backbench MPs.

You can't say 'whatever happens' ... on all issues I expect to remain a member of the government Clare Short International Development Secretary

Further opposition came from Church of England bishops who delivered their sternest message yet against war.

But Mr Blair, who will meet US President George Bush later this month, refused in public or private to give the guarantee the doubters want - that he will not back unilateral American action against Iraq.

In a new interview, cabinet minister Clare Short has refused to rule out resigning if the UK backs unilateral action.

In the Commons, Mr Blair dismissed "conspiracy theories" suggesting the threat of war was really about oil supplies.

'Unpopular' words

Mr Blair again warned the chemical, biological or nuclear weapons could fall into terrorist hands if left unchecked.

He continued: "This is a difficult time and I understand the concerns that people have."

"But sometimes prime ministers have to say the things people do not want them to say but we believe are necessary to say.

A fresh UN resolution is absolutely essential if this military action is to be morally justified Richard Harries Bishop of Oxford

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"Because the threat is real and if we do not deal with it, the consequences of our weakness will haunt future generations."

He dismissed "conspiracy theories" suggesting the threat of war was really about oil supplies.

Mr Blair also denied Conservative claims there were divisions between himself and International Development Secretary Clare Short.

Ms Short has said the UK should not back any action without a second UN resolution.

The prime minister instead says an "unreasonable or unilateral" block would not be allowed to confine other nations.

Short's stance

In an interview to be published in this week's New Statesman, Ms Short is asked if she would stay and argue her case in the cabinet if military action went ahead without new UN approval.

She replies: "You can't say 'whatever happens' ... on all issues I expect to remain a member of the government.

"I have to broadly agree with what the government's doing."

But Ms Short insisted neither the cabinet nor her party were divided as all wanted to reinforce the UN.

Earlier, Mr Blair faced a barrage of questions from backbenchers about Iraq at a meeting of the Parliamentary Labour Party.

Labour Chairman John Reid said MPs had show their "overwhelming support" for Mr Blair at the meeting.

But former ministers Glenda Jackson and Peter Kilfoyle were among those MPs leaving the meeting saying they were unconvinced.

Worries about Iraq come ahead of expected disquiet over a government announcement that it is "minded" to support America's controversial 'Son of Star Wars' missile defence programme.

Moral critique

Church of England bishops have also reiterated their opposition to military action in Iraq.

The Bishop of Birmingham said the government was looking to act as "judge, jury and executioner".

Peace campaigners have meanwhile blocked road access to HMS Ark Royal, which is in Loch Long in Scotland, before heading for the Gulf.

A Ministry of Defence spokeswoman said the aircraft carrier was almost fully loaded and the protesters were not interfering with operations.

Time warning

General Wesley Clark, Nato's former Supreme Commander Europe, predicted a war on Iraq was likely to start in mid to late February.

The general told BBC Radio 4's Today programme he did not think the US Administration would want to wait for another UN Security Council resolution before taking action.

US President George Bush is warning "time is running out" for Iraqi leader Saddam Hussein to surrender the weapons of mass destruction which the US believes he owns.

"I'm sick and tired of games and deception," said Mr Bush.

Mr Blair is reportedly to meet the US president in America later this month, after weapons inspectors report to the UN.