A seven-year inquiry into the UK's involvement has concluded that London failed to exhaust all peaceful options. Ex-premier Tony Blair said he assumes "full responsibility" for any mistakes that arose from the conflict.
The UK's Iraq Inquiry Chairman John Chilcot, a retired civil servant, on Wednesday said Britain's decision to go to war in Iraq was "based on flawed intelligence" during the release of the committee's long-awaited report on the Iraq War.
"We have concluded that the UK chose to join the invasion of Iraq before the peaceful options for disarmament had been exhausted. Military action at that time was not a last resort," Chilcot said.
"Despite explicit warnings, the consequences of the invasion were underestimated. The planning and preparations for Iraq after Saddam [Hussein] were wholly inadequate," he noted.
In 2003, British forces joined the US invasion of Iraq, which eventually led to the capture of the late Iraqi leader Saddam Hussein.
Prior to the invasion, London had joined Washington in alleging an "imminent threat" from weapons of mass destruction. However, the inquiry found Hussein posed "no imminent threat."
In 2009, former British Prime Minister Gordon Brown announced that an inquiry would be conducted to identify lessons that could be learned from the UK's involvement in the Iraq War.
"We have concluded that the circumstances in which it was decided that there was a legal basis for UK military action were far from satisfactory," Chilcot said.
"The government's preparations failed to take account of the magnitude of the task of stabilizing, administering and reconstructing Iraq, and of the responsibilities which were likely to fall to the UK," Chilcot said.
"The UK military role in Iraq ended a very long way from success," he added.
Chilcot oversaw the inquiry, which took seven years to complete, heard from over 100 witnesses and analyzed more than 150,000 documents.
Former British Prime Minister Tony Blair, who pushed for the UK's involvement in the invasion, said on Wednesday that he takes "full responsibility for any mistakes without exception or excuse."
"The report should lay to rest allegations of bad faith, lies or deceit. Whether people agree or disagree with my decision to take military action against Saddam Hussein; I took it in good faith and in what I believed to be the best interests of the country," he said in a statement issued after the report's release.
"The inquiry does not make a finding on the legal basis for military action but finds that the attorney general had concluded there was such a lawful basis by 13 March 2003," he added.
In 2002, Blair told former US President George W. Bush that he would support him in the run-up to the invasion.
"I will be with you, whatever," Blair said.
'Lessons for the future'
Meanwhile, Prime Minister David Cameron said Chilcot's findings need to be thoroughly reviewed, saying two days would be set aside next week in the House of Commons, the lower house of parliament, to debate the report's contents.
"I think the most important thing we can do is to really learn the lessons for the future and the lessons he lays out quite clearly," Cameron said, referring to Chilcot's report. "The only point I would make is that there is actually no set of arrangements and plans that can provide perfection in any of these cases."
ls/msh (AFP, AP, Reuters)