Matthew Jury, a lawyer representing families who lost loved ones in the conflict, said his clients are "of course saddened that it appears to have been confirmed that their loved ones died unnecessarily and without just cause or purpose."
Sarah O`Connor, whose brother was killed in the war, said she was angry that "11 and a half years of healing" had been undone.
"I`ve gone back to that time when I learned that my brother had been killed." she said."And there is one terrorist in this world that the world needs to be aware of, and it`s Tony Blair -- the world`s worst terrorist."
The families would be examining the 2.6 million-word Chilcot report to see whether it forms the basis of any legal proceedings, they said.
In the face of fierce criticism from a British inquiry into the Iraq War, Tony Blair, Britain`s leader at the time, says he will respond fully later Wednesday, but still believes "it was better" to topple Iraq`s former dictator.
"I will at the same time say why, nonetheless, I believe that it was better to remove Saddam Hussein and why I do not believe this is the cause of the terrorism we see today, whether in the Middle East or elsewhere in the world," he said.
He said that the Chilcot 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 noted that the report had found that there had been "no falsification or improper use of intelligence," "no deception of Cabinet," and "no secret commitment" between Blair and then-U.S. President George Bush to go to war.
"Military action in Iraq might have been necessary at some point, but in March 2003 there was no imminent threat from Saddam Hussein," John Chilcot, chairman of a British inquiry into the UK`s role in the Iraq War, said Wednesday.
The "strategy of containment" could have continued for some time, he said.
Speaking ahead of the release of the long-awaited report in London, Chilcot said former British Prime Minister Tony Blair was warned of the risks of regional instability and the rise of terrorism before the invasion of Iraq, but pressed on regardless.
The UK failed to appreciate the complexity of governing Iraq, and did not devote enough forces to the task of securing the country in the wake of the invasion, he said.
Blair`s decision to invade Iraq was influenced by his interest in protecting the UK`s relationship with the United States, he said.
That relationship "does not require unconditional support where our interests and judgments differ," said Chilcot.
The inquiry did not express a view on whether the invasion was legal, he said, arguing that that was a decision for another forum.
John Chilcot, chairman of a British inquiry into the country`s role in the Iraq War, said in releasing the report that Britain joined the invasion of Iraq "before the peaceful options had been exhausted," and that preparations for the aftermath were "wholly inadequate."
UK policy was based on "flawed intelligence and assessments," he said. "They were not challenged and they should have been."
Hindsight was not necessary to identify the risks of what would happen to the country post-invasion, he said: "The risks... were each explicitly identified before the invasion."
Furthermore, the legal basis for the war was "far from satisfactory," he said.
"The people of Iraq have suffered greatly," he said.
Britain`s long-awaited inquiry into the country`s involvement in the Iraq War will be released Wednesday, placing former Prime Minister Tony Blair`s actions in leading the country into a deeply unpopular conflict under comprehensive scrutiny.
Protesters began gathering outside the London office building where the report is to be released at 11 a.m. local time (6 a.m. ET) Wednesday, as the politicians who launched the deadly invasion more than 13 years ago -- most notably Blair -- braced themselves for the fallout from the report.
The Iraq Inquiry -- widely known as the Chilcot report, after inquiry chairman John Chilcot -- was commissioned in June 2009 by Blair`s successor, Gordon Brown, following pressure from the public and parliament.
Charged with examining the build-up to the conflict, the war itself and its bloody aftermath -- over a period from 2001 to 2009 -- the inquiry was initially expected to take a year to complete.
Instead it has taken more than seven -- longer than the war itself -- with the final report running to 2.6 million words across 12 volumes.
Long shadow of invasion
Britain`s decision to go join the U.S.-led invasion of Iraq in March 2003 was perhaps its most controversial foreign policy decision in the modern era.
Britain`s Parliament approved the war -- ostensibly to remove Saddam Hussein and rid the country of weapons of mass destruction (WMD) -- shortly before the invasion, although U.N. approval was not gained and millions marched in the streets in protest.
Hussein was removed and later executed. But the WMD threat was found to have been exaggerated and the promise to turn a dictatorship into a democracy was never delivered on.
Instead, the country descended into years of vicious sectarian conflict, with large swathes seized by terror group ISIS.
More than 250,000 people have died violent deaths since the 2003 invasion, according to the Iraq Body Count project, while millions of Iraqis have been made homeless in the conflict with ISIS.
On the British side, 179 service personnel were killed in the conflict.
Calls for further action against Blair
Blair is expected to give a statement some time after the release of the report today, as is outgoing prime minister David Cameron, who supported the war as a backbench MP, and Labour leader Jeremy Corbyn, who fervently opposed it.
There have been calls for Blair -- who gave evidence to the inquiry twice -- to be charged with war crimes over Iraq, but it is considered unlikely that the report will issue a decision on the legality of the war.
Speaking to British broadcasters on Tuesday night ahead of the launch of the report, Chilcot, a retired senior civil servant, said the report would not avoid criticizing key figures where warranted.
"I made very clear right at the start of the inquiry that if we came across decisions or behavior which deserved criticism, then we wouldn`t shy away from making it," he said. "Indeed, there have been more than a few instances where we are bound to do that.
"But we shall do it on a base of a rigorous analysis of the evidence that supports that finding. We are not a court -- not a judge or jury at work -- but we`ve tried to apply the highest possible standards of rigorous analysis to the evidence where we make a criticism."
An overriding aim of the inquiry will be to ensure Britain never goes to war in future without having made a comprehensive assessment of the situation, he said.
Key issues
One key issue expected to be addressed in the inquiry, which had access to a redacted version of Blair and then-U.S. President George W. Bush`s communications: what was said between the leaders in the build-up to the invasion?
What were the circumstances surrounding then attorney general Peter Goldsmith`s change of heart over the legal footing of the war? (He initially said that further U.N. Security Council approval was needed, before changing his stance days ahead of the invasion.)
And did Britain`s military commanders fail to adequately prepare for the war and its aftermath?
The report is embargoed until after Chilcot makes a public statement at its release, but an embargoed version has been provided to a group including politicians, journalists and the families of victims -- some of whom have already expressed fears that the report will be a whitewash.
CNN political contributor Robin Oakley said, after seven years in the making, the report may fail to live up to the high expectations some held out for it that it would bring leaders to account for the war.
"It started in an age when you could keep things much more covered in terms of what goes on in government," he said.
"Now expectations worldwide have been raised in terms of the amount me expect to know about how decisions are taken... I think in those terms, it might be a disappointment."
The reputations of many of the key figures under scrutiny had already taken a hammering in the eyes of the public the intervening years, he said.
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