A leak which means the Government must explain Attorney General's change of heart

The content of the Attorney General's legal advice has been the subject of fevered speculation ever since Tony Blair took the decision to support President Bush and go to war.

The content of the Attorney General's legal advice has been the subject of fevered speculation ever since Tony Blair took the decision to support President Bush and go to war.

The UN secretary general, Kofi Annan, and many international lawyers have all asserted that without a second UN resolution, the push to military action was not authorised under international law.

In the past few days the legality of war has become a central question in the election campaign with Charles Kennedy and his Liberal Democrat deputy, Sir Menzies Campbell, a QC, both arguing that Mr Blair prosecuted an illegal war.

Lord Goldsmith's assertion that the use of force against Iraq was legal - an assessment made in a one-page written reply to a question in the House of Lords - is seen as a minority view in legal circles.

There have been consistent calls for the Government to set the record straight by publishing the full advice. MPs and newspapers - including this one - have applied under the Freedom of Information Act to see the legal advice. But they have been blocked by Whitehall.

Yesterday's leak to Channel 4 News will prove acutely embarrassing for ministers, because it shows the legality of the invasion was not clear cut at all. It also demonstrates clearly that in the space of 10 days the Attorney General changed his mind. On 17 March 2003, Lord Goldsmith stated unequivocally that the use of force would be justified under international law. He set out his reasons in a one-page parliamentary answer to MPs and peers.

Only 10 days before, Lord Goldsmith produced the fuller document for Mr Blair - leaked last night - in which he stopped short of giving a definitive view on whether war would be legal, and said it might be safer to secure a second UN resolution.

What happened in those few days? Lord Goldsmith has always denied he was "leaned on." Now this opinion is in the public domain the Government will find it harder to resist giving an explanation about why the Attorney General had such a rapid change of heart.

But it was disclosed in Lord Butler's inquiry last July that before offering his legal view he sought from Mr Blair an assurance that Saddam Hussein was in breach of existing United Nations resolutions. He gained these assurances from Mr Blair. The question now is: What exactly did Mr Blair say to him?

In a book by the lawyer Phillipe Sands it emerged that the Attorney General also held a meeting with two political allies of Mr Blair about the war. The meeting with Lord Falconer of Thoroton and Baroness Morgan of Huyton is not believed to have been minuted.

What is clear is that the Attorney General's final view that war was legal was not shared by other lawyers in the Government. Foreign Office lawyers concluded the invasion would be illegal without a second resolution.

The legal countdown

* 7 March 2003: Lord Goldsmith delivers 13-page paper detailing status of UN resolutions on Iraq to the Prime Minister. It gives no definitive view on the legality of an attack, but says it would be "safer" to seek a further reference to the UN.

* 13 March 2003: Lord Goldsmith tells Lord Falconer, then a Home Office minister, and Baroness Morgan, Mr Blair's director of political and government relations, at an "informal meeting" that an attack would be legal without a further UN resolution.

* 14 March 2003: Lord Goldsmith's legal secretary writes to Mr Blair's private secretary asking for confirmation that "it is unequivocally the Prime Minister's view that Iraq has committed further material breaches as specified in ... resolution 1441". Lord Goldsmith said it was essential that strong evidence existed that Iraq was still producing weapons of mass destruction.

* 15 March 2003: Mr Blair's private secretary replies: "It is indeed the Prime Minister's unequivocal view that Iraq is in further material breach of its obligations."

* 17 March 2003: US, UK and Spain withdraw proposal for a new Security Council resolution. UK blames France for threatening veto. Lord Goldsmith gives two-page document to Cabinet saying war would be legal. Lord Goldsmith issues a statement in Parliament saying an attack on Iraq would be lawful.

* 18 March 2003: Elizabeth Wilmshurst, deputy legal adviser to Michael Wood at the Foreign Office, resigns in protest over the legality of the war, saying it would be a "crime of aggression".