The order to send 45,000 British troops to take part in the 2003 invasion to topple Saddam Hussein has always been controversial and led to massive anti-war protests in London.
During meetings with the inquiry committee held before the formal hearings begin, relatives of British soldiers killed during the conflict accused Blair of taking Britain into an illegal war and deceiving the public.
A government dossier justifying military action before the war included the claim that Saddam was capable of launching weapons of mass destruction within 45 minutes.
No such weapons were found, leading to accusations that Blair had distorted intelligence. Inquiry chairman John Chilcot said the five-member inquiry committee would start public hearings on 24 November before moving on to questioning senior politicians in January.
"We will use the first five weeks of hearings to help establish a reliable account of the essential features of the UK's involvement in Iraq," the former civil servant said in a statement.
The panel will start by hearing from senior officials and military officers who advised ministers or helped shape government policies, and how those policies were communicated.
"That will give us a clear understanding of how policy developed and was implemented; and what consideration was given to alternative approaches," Chilcot said, adding the committee would consider the legal basis for war.
"Early in the New Year, we shall begin taking evidence from ministers, including the former prime minister, on their roles and decisions."
Chilcot has not yet said whether Prime Minister Gordon Brown would be among those called to testify.
Blair will cooperate fully
A spokesman for Blair, now Middle East peace envoy and a possible candidate to be the European Union's first president, has said he would cooperate fully with the inquiry. Brown initially said hearings would be held in private because of national security concerns, but Chilcot reaffirmed that private sessions would only be held to discuss "sensitive" issues or evidence from junior officials.
A second round of public hearings is scheduled for the middle of 2010 after parliamentary elections to ask witnesses to "discuss issues in more detail" or to follow other lines of inquiry.
Chilcot, who said he hoped the committee would be able to deliver its conclusions by the end of next year, stated that the inquiry was not a trial or a judicial inquiry. "I have, however, made clear that we will not shy away, in our report, from making criticisms - of individuals or systems - where that is warranted," he said.
(EurActiv with Reuters)
