The admission by the man who, as Lord Chancellor, helped make the case for the war for the Blair government in the Lords in 2003, comes amid increasing concerns that the Iraq inquiry chaired by Sir John Chilcot may not report until next year despite being launched six years ago.
Speaking in a BBC documentary about the fall of Labour in Scotland, Charles Falconer, who was born in Edinburgh and went to the prestigious Glen-almond College in Perthshire, pinned much of the blame on the “perception” of the Iraq war that many now believe was illegal.
He said: “We didn’t find weapons of mass destruction there and that was the basis by which we went in.
“So on that basis, we weren’t right to go in.”
Mr Blair’s former flatmate, when the two were starting out as barristers in the 1970s, admitted that the ex-Prime Minister also believes that.
He said: “I think the Iraq war damaged Labour everywhere, and I think that the Iraq war is perceived to be a mistake.”
Asked who thought it was a mistake, he said: “By Labour, by Tony Blair.
“That damaged Labour right throughout Scotland and England, but I’m not sure that it necessarily damaged Labour more in Scotland than it did in England.”
Asked whether now both he and Mr Blair regarded it as a mistake, Lord Falconer said: “Well, what I’m saying is, it did do us some damage. I supported the invasion.” The war began in 2003 with the UK supporting the US president’s decision to invade Iraq,
This followed a failed attempt to get support for military action through the United Nations with France, Russia and China vetoing a resolution that would have authorised it.
However, both the UK and US governments claimed that an earlier resolution allowed them to invade when Saddam Hussein failed to comply with weapons inspectors.
MPs voted to support the war but many believe that this was done on the basis of a “dodgy dossier” produced by the Labour government which suggested that Iraq could use weapons of mass destruction against the UK.
While the invasion succeeded quickly, the coalition forces had to deal with insurgencies until they withdrew in 2011 after installing a democratic Iraqi government.
By then 4,809 allied troops were killed, including 179 from the UK, and an estimated 158,000 Iraqi citizens were killed.
Opposition to the war was strong in the UK.
A few weeks before the invasion began, hundreds of thousands of people took to the streets in cities across Britain in protest against the proposed war.
Police at the time said the London march alone was the UK’s biggest ever demonstration with at least 750,000 taking part, although organisers put the figure even higher, at closer to two million.
While Mr Blair still won the election in 2005, Labour’s majority fell and instead there was an all-time high number of seats for the Lib Dems who had opposed the invasion.
Then in 2007, Alex Salmond led the SNP to defeat Labour in the Holrood election with resentment against the war increasing, as news of casualties continued and with the government forced to admit that no weapons of mass destruction would be found.
Last night, the SNP, which strongly opposed the war from the start along with the Lib Dems, described Lord Falconer’s words as “shocking”.
Brendan O’Hara MP, the SNP’s defence spokesman in Westminster, said: “This is a quite stunning revelation.
“Twelve years after the Westminster government waged the illegal and immoral war on Iraq, Lord Falconer, who is a close ally of Tony Blair, has admitted that the Labour government - backed by the Tories - were wrong to go to war. “Of course, the SNP and many others were saying back then that there were no weapons of mass destruction - and therefore no justification for the war - but the establishment would not listen.”
However, Mr O’Hara said the comments reinforce the need for the Chilcot inquiry to be published after reports that it has become bogged down in legal requirements to allow people who have been criticised in it to have a right of reply.
Mr O’Hara said: “It is now six long years since the Inquiry led by Sir John Chilcot started to take evidence from witnesses involved in the period leading up to the illegal invasion of Iraq, at a cost of £10 million.”
He added: “The UK Government has a moral and political responsibility for getting to the bottom of this calamitous war and its consequences.
“This inquiry needs to be published in full - and as a matter of urgency.”