Lord Steyn, who retired last month as a judge sitting in the UK's highest court, described the invasion of Iraq as "military folly" and accused the Government of "scraping the legal barrel" in trying to justify it.
The former law lord told an audience of lawyers and civil rights campaigners in London that it was wrong for the Prime Minister to have called the rule of law a "game".
He said: "The maintenance of the rule of law is not a game. It is about access to justice, fundamental human rights and democratic values."
He added: "After the recent dreadful bombings in London we were asked to believe that the Iraq war did not make London and the world a more dangerous place. Surely, on top of everything else, we do not have to listen to a fairy-tale."
Lord Steyn praised Walter Wolfgang, who was detained under anti-terrorism legislation after protesting about the war in Iraq at the Labour Party's annual conference in Brighton.
"One knows, of course, that the Government earnestly desires a closure on this issue [Iraq]. But that is not possible: while there are different views on this occasion, even Mr Walter Wolfgang would be free to express the opinion for which he was charged under the Terrorism Act. Possibly his name will live on when the names of some now in charge of affairs are forgotten."
Lord Steyn, speaking upon his appointment as the new chairman of Justice, the civil rights group, went on to condemn the Government's legal justification for war. He said he agreed with his predecessor, Lord Alexander of Weedon QC, who in his 2003 annual lecture concluded that in its search for a justification in law for war the Government was driven to "scrape the bottom of the legal barrel".
Lord Steyn, a South African-born judge, also said he agreed with Lord Alexander's analysis that there were "no current links between the odious Saddam Hussein regime and al-Qa'ida".
Lord Steyn added: "He [Lord Alexander] analysed the constantly shifting grounds for intervention. Rightly he concluded that none of those grounds had any plausibility. He showed that ... the earlier Resolution 678, preceding the driving of Iraq from Kuwait 12 years earlier, had no relevance to the contemporary international position. The sole reason for harking back to it was that it was impossible to obtain Security Council approval for intervention in Iraq."
Yesterday the Lord Chancellor, Lord Falconer of Thoroton, defended his decision to appoint a senior judge to a court in Wales. The Judicial Appointments Commission criticised the selection of Wyn Williams QC to run the chancery division in Wales because he lacked specialist experience in chancery work, which covers land disputes, trust law and commercial matters. But giving evidence to the Commons Constitutional Affairs Committee, Lord Falconer said: "I have absolutely no doubt whatsoever that the appointment I made was the right one. I am happy to say that both myself and the Lord Chief Justice take the view that he has been very successful in that job. For the Judicial Appointments Commission to say it was inappropriate was, in my view, completely wrong. I don't think that they properly analysed the material. I think they got the whole thing out of perspective and produced a very inaccurate and unfairly damaging report."
Lord Falconer acknowledged that Mr Williams had once visited his house, but dismissed suggestions that he knew him well. "He did apparently come to my house 20 years ago for a party somebody gave for somebody that we both knew," he said, and they had met three or four times since.Reuse content