The attorney general has been drawn into a fresh row over whether he dropped earlier objections in order to authorise the war with Iraq.

Lord Goldsmith has been at the centre of a continuing row over the nature of his legal opinion justifying the use of force.

Renewed speculation followed the release, under the Freedom of Information Act, of the resignation letter of the Foreign Office's deputy legal adviser.

Elizabeth Wilmshurst, in her letter of March 18, 2003, wrote of a possible war that "an unlawful use of force on such a scale amounts to the crime of aggression".

However, one paragraph of the letter was blacked out prior to its release to news organisations.

Channel 4 News said the missing section read: "My views accord with the advice that has been given consistently in this office, before and after the adoption of UN security council resolution 1441.

"And with what the attorney general gave us to understand was his view prior to his letter of 7th of March.

"The view expressed in that letter has of course changed again into what is now the official line."

The letter appears to confirm previous reports that as late as March 7, 2003 Lord Goldsmith was of the belief that war would be illegal.

However, on March 17 he issued a written statement setting out a legal basis for the war.

'Damning evidence'

Shadow foreign secretary Michael Ancram said ministers were "trying to save their own skin and I think they have scored an enormous own goal".

"What they have done is not to decrease the amount of doubt and mistrust that there is about the way that the government handled the run-up to the Iraq war, but actually increased it.

"This is damning evidence, unless it is explained."

"If there was a reason why the attorney general changed his mind between March 7 and March 17, then we should be told about it.

"What is happening at the moment is that the government is trying desperately to cover its tracks."

Liberal Democrat foreign affairs spokesman Sir Menzies Campbell also told Channel 4 News that a section of the resignation letter had been blacked out "not in the public interest, but in the government interest".

"The government is severely embarrassed by the fact that there is continuing controversy about the legal advice given by the attorney general and the way in which he arrived at his final opinion," he added.

'Clear views'

Speaking on Wednesday night, a spokesman for the attorney general said Lord Goldsmith had made clear that the decision on the legality of the war was made independently.

And the Foreign Office said the missing paragraph from the resignation letter had been legitimately withheld.

"Elizabeth Wilmshurst's resignation minute was disclosed by the Foreign and Commonwealth Office today under the Freedom of Information Act," the department said in a statement.

"Two sentences were redacted by the FCO from the document because their content related to the provision of legal advice in relation to the use of force against Iraq.

"Regardless of whether these references were accurate, this information was therefore covered by exemptions in the Act which apply to confidential legal advice, sections 42(1) and 35(1)(c) of the Act, and the formation or development of government policy, section 35(1)(a)."