In evidence to the Iraq inquiry, Lord Goldsmith, who at the time was the government’s top legal adviser, disclosed that he was “uncomfortable” about statements made by the then-prime minister in the run up to the 2003 invasion.
Two months before the war began, in a meeting at No 10, the former attorney general told Mr Blair that war would not be legal without a fresh mandate from the UN.
In a statement to MPs the following day, however, the Labour prime minister said that there were “circumstances” in which an attack could be valid.
The following month, he gave an interview in which he suggested that war would be legal if another nation had made an “unreasonable” veto at the UN on military action.
A witness statement to the Chilcot Inquiry into the war, published today, makes clear that Lord Goldsmith considered that this did not accord with the advice he had given Mr Blair.
Asked whether Mr Blair’s words were compatible with the advice he received, the former attorney general wrote simply: “No.”
He added: “I was uncomfortable about them (the prime minister’s comments) …
“My concern was that we should not box ourselves in by the public statements that were made, and create a situation which might then have to be unravelled.”
Lord Goldsmith evidence to the inquiry has come under scrutiny after he admitted changing his mind about the legality of military action on the eve of the war.
His views were swayed during meetings he was encouraged to have with American government lawyers and Sir Jeremy Greenstock, Britain’s ambassador to the UN.
Giving evidence to the inquiry last year, he denied that he was “leant on” by No 10 to change his legal opinion.
Until two weeks before the invasion, in March 2003, Lord Goldsmith had been of the view that UN resolution 1441, which was passed in November 2002 and declared Iraq in “material breach” of its obligations to disarm, was not sufficient to sanction war by the UK and United States.
In the new evidence to the inquiry, Lord Goldsmith said in his statement that the phrasing of resolution 1441 was “problematic”.
He was not actively consulted on the final drafting of the resolution after telling Mr Blair in October that the text as it stood did not authorise the use of force.
The former attorney general said: “I was not being sufficiently involved in the meetings and discussions about the resolution and the policy behind it that were taking place at ministerial level.
“Much of the later difficulties could have been avoided if my view had been sought on the drafts that were developed during the later stages of the negotiations, particularly bearing in mind the fact that I had not been persuaded that the early drafts achieved our objectives.”
The Chilcot Inquiry also released a previously secret memo in which Jack Straw, the former foreign secretary, warned Mr Blair of the “high” risks of his visit to US President George Bush’s ranch in Crawford, Texas.
In the letter, dated March 25 2002, Mr Straw said: “A legal justification is a necessary but far from sufficient precondition for military action.
“We also have to answer the big question – what will this action achieve? There seems to be a larger hole in this than on anything.”
The former foreign secretary said there was no certainty the regime that replaced Saddam would be any better, adding: “Iraq has had no history of democracy so no one has this habit or experience.”
Mr Blair will appear before the inquiry for a second time on Friday, when he will be asked to explain gaps in his earlier evidence and discrepancies between his account and official documents and other witnesses’ testimony.
A spokesman for Mr Blair said: “Tony Blair will deal with all these issues in his evidence on Friday. The issue of the so called unreasonable veto was not the basis on which Britain took part in the military action. The basis was that given in the Attorney General’s advice which he has confirmed in the statement published today. What Peter Goldsmith’s statement does is make it categorically clear that there was a proper legal basis for the military action taken.”