Clare Short, the International Development Secretary, stunned the Government last night by declaring she would resign from the Cabinet if Tony Blair went to war on Iraq without a new UN mandate.
Ms Short warned Mr Blair that he was being "extraordinarily reckless" with global security and his own future as Prime Minister by thinking of going it alone with President George Bush.
Coming as he launches a last push for a second UN resolution, the timing and bitterness of her remarks will infuriate Mr Blair and are bound to provoke calls for her dismissal.
When asked on BBC Radio 4's Westminster Hour if she would quit if there was no new UN resolution, she replied: "Absolutely, there's no question about that." And she added another condition for her to remain in post: that the rebuilding of Iraq had to be led by the UN rather than the US.
Ms Short said: "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."
The Prime Minister's official spokesman made clear Downing Street's surprise at the remarks, pointing out that she had not made such views clear to Mr Blair, even in private.
Ms Short will face claims that she set out to undermine Mr Blair after it emerged that the interview was unplanned and she initiated the contact with the BBC.
Meanwhile Mr Blair suffered his first resignation over the issue yesterday when Andrew Reed, parliamentary private secretary to Margaret Beckett, the Environment Secretary, quit in protest at the lack of time being given to UN weapons inspections.
Government sources have in recent weeks claimed that Ms Short would not resign over the issue and wanted to work to achieve the best humanitarian situation possible in a conflict. But Ms Short said it was "time for cards on the table" and insisted she could not stay in government and "defend the indefensible".
Asked whether Mr Blair had acted recklessly, 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 ... 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 added: "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."
Ms Short, who resigned from Labour's opposition front bench over the party's support for the Gulf War in 1991, said that after a cabinet meeting two weeks ago, Mr Blair's press office declared "absolutely rock solid" backing from fellow ministers, despite Ms Short making clear her concerns over a second resolution.
"What worries me is that we have detailed discussions either personally or in the Cabinet and then the spin the next day is: 'We're ready for war.' So I'm worried now that people like me are being told, 'Yes, all this is under consideration,' but we're on a different path."
Chris Patten, the European commissioner for external relations, said Britain and the US would not be able to call on EU funding for the reconstruction of Iraq if they attacked and occupied the country without a UN mandate.
In an interview with The Independent, Mr Patten said it would be politically impossible for the EU to make money available to rebuild Iraq, given the divisions that have emerged over how to disarm Saddam Hussein.
© 2003 Independent Digital (UK) Ltd