International Development Secretary Clare Short signalled last night that she will resign from the Government if Britain goes to war against Iraq without United Nations backing.

After weeks of speculation about her position on the Iraqi crisis, Ms Short said it was now "ten minutes to midnight" - and time to make her intentions clear.

Interviewed on BBC Radio 4's Westminster Hour, Ms Short suggested Prime Minister Tony Blair's hardline position over Saddam Hussein was "reckless".

Her outright stand will come as another hefty blow to Mr Blair, who earlier yesterday endured the first Government resignation over his Iraqi strategy, even as he struggled to muster international support.

Loughborough MP Andrew Reed quit as unpaid Parliamentary Private Secretary to Environment Secretary Margaret Beckett, insisting that the UN had to provide the route for resolving the crisis.

There is mounting speculation that more senior members of the Government could resign.

Ms Short, asked if she would consider resigning if there was no mandate from the UN for war, said: "Absolutely, there's no question about that."

She continued: "If there is not UN authority for military action or if there is not UN authority for the reconstruction of the country, I will not uphold a breach of international law or this undermining of the UN and I will resign from the Government.

"I think it's time for cards on the table. People are speculating and making all sorts of statements about my intentions."

Asked whether she thought Mr Blair had acted rather recklessly over Iraq, she said: "I'm afraid that I think the whole atmosphere of the current situation is deeply reckless; reckless for the world, reckless for the undermining of the UN in this disorderly world, which is wider than Iraq - (which) the whole world needs for the future - reckless with our Government, reckless with his own future, position and place in history.

"It's extraordinarily reckless, I'm very surprised by it."

She continued: "My own view is that allowing the world to be so bitterly divided; the division in Europe, the sense of anger and injustice in the Middle East is very, very dangerous. We're undermining the UN, it's a recruiting sergeant for terrorism, there's a risk of a divided world, with a weakened UN, and we shouldn't be doing it like this."

Asked whether Mr Blair and Foreign Secretary Jack Straw were aware of her concerns she said: "I have a good relationship and frequent discussions with both of them."

A Downing Street spokesman said Ms Short had not expressed the views ascribed to her in advance to Mr Blair.