Try as it might, the Government cannot escape from the shadow of Iraq. Yesterday, the resignation letter of Elizabeth Wilmshurst, the former deputy legal adviser at the Foreign Office, was released under the Freedom of Information Act. Ms Wilmshurst resigned in March 2003 because she could not support what she saw as an illegal invasion. The letter itself was heavily censored, but Channel 4 news managed to get hold of the full text. What it contains is of the utmost importance.

Try as it might, the Government cannot escape from the shadow of Iraq. Yesterday, the resignation letter of Elizabeth Wilmshurst, the former deputy legal adviser at the Foreign Office, was released under the Freedom of Information Act. Ms Wilmshurst resigned in March 2003 because she could not support what she saw as an illegal invasion. The letter itself was heavily censored, but Channel 4 news managed to get hold of the full text. What it contains is of the utmost importance.

Ms Wilmshurst's letter demonstrates that the advice of the Attorney General as to the legality of the invasion of Iraq was indeed changed, just as many suspected. It raises - yet again - the serious implication that Lord Goldsmith was leant upon by Downing Street to give the ruling that the Prime Minister wanted to hear.

The Government has been asked many times to reveal the full legal advice that it was given by the Attorney General. This has always been refused on the grounds that this advice is confidential. When it emerged that even the Cabinet was not shown the full advice, the Government claimed - bizarrely - that there was, in fact, no full advice further to what was shown to Parliament. This resignation letter throws us into even greater confusion. The Government will continue to be dogged by these suspicions until it releases all the documentation relevant to the Attorney General's advice.

This revelation came on the same day as the chronic mishandling of the occupation of Iraq was laid bare by the Commons Defence Select Committee. The committee's report does not make for comforting reading. The rash decision to disband the Iraqi army and police force has proved disastrous. The loss of vital time in training Iraqi forces now means there is no prospect of a British troop withdrawal until 2006 at the earliest.

Yesterday, the scale of the Government's mismanagement of the whole Iraq affair stood revealed. The public and Parliament have a right to know the legal authority for the invasion. Until the Prime Minister offers the full facts, the questions and doubts will continue to haunt him.