Apart from the overthrow of Saddam Hussein, the invasion of Iraq had turned into "a tragedy", former United Nations chief weapons inspector Dr Hans Blix said during a visit to Dublin.
He described the intelligence reports used to justify the invasion as "fake-based".
"A brutal dictator was toppled. The rest remains a tragedy. How could it happen?" Dr Blix asked an audience at the Institute of European Affairs.
A former Swedish foreign minister, Dr Blix came into sharp conflict with the Bush administration and its allies in 2003 because he did not corroborate their claim that Saddam possessed weapons of mass destruction.
However, Dr Blix was seen to be vindicated after the invasion, when no stockpiles of weapons were discovered.
"The disasters in Iraq and Lebanon show the consequences of an exaggerated belief in and reliance on military surgery," he said yesterday.
"The war in Iraq also shows us the consequences of ignoring international fact-finding. Rarely have the reports of international fact-finders, views of NGOs and public opinion been as ignored as before the invasion of Iraq in March 2003. The world was told that the invasion would lead to the 'moment of truth'. It did, and the truth was that there were no weapons of mass destruction.
"Most had been destroyed already in the early 1990s. In 2003 a state and a people were thus sentenced to war and invasion on erroneous grounds, on 'faith-based' - even 'fake-based' - intelligence."
He outlined the scenario which led to the invasion as follows: "A few spies and many defectors became chief sources of information, and misleading reports were accepted by governments that looked for arguments for armed action more than truth."