The publication this week of the long awaited Chilcot inquiry report into the Iraq war is set to be a "defining moment of truth" for Tony Blair Scotland's First Minister believes.

Nicola Sturgeon said the families of those killed or wounded in the Gulf conflict needed to have confidence that the "full picture is given" when the official verdict is delivered on the UK's role in the invasion and occupation this Wednesday.

Sturgeon told the Sunday Herald that the findings would have far-reaching implications for Blair, whose Labour government took the decision to join the United States-led campaign in Iraq during the presidency of George W Bush.

Former Liberal Democrat leader Menzies Campbell said Sir John Chilcot's report will reveal a "far greater understanding" about intimate political exchanges between Blair and Bush and show that they conspired to ignore public opinion opposing the invasion of Iraq.

Lord Campbell, who was a leading opposition voice during Westminster's decision to go to war in 2003, said he expected the findings to shed much greater light on how Bush and Blair cooperated to make the political case for the allied invasion, suggesting that they briefed each other about the extent of domestic opposition to it.

He said he expected it to show how "everything was subordinate" to Blair and Bush's decision to go to war, including overwhelming opposition to it with mass demonstrations like the one million strong protest in London in February 2003. Campbell added that Chilcot may also state a more "sustained and coherent criticism" of those other than Blair who were involved in decision making, which sources have suggested will include Jack Straw, the Foreign Secretary at the time of the invasion.

Chilcot is expected to focus on the decision-making behind the conflict. which was launched by the US with strong UK backing, which Blair and Bush said was made "to disarm Iraq of weapons of mass destruction, to end Saddam Hussein's support for terrorism, and to free the Iraqi people".

The conflict led to the deaths of tens of thousands of Iraqi civilians, with no weapons of mass destruction ever found.

There have also been calls for Blair, who was in office between 1997 and 2007, to be prosecuted for breaching his constitutional duties and taking the UK into a conflict that resulted in the deaths of 179 British troops.

Former SNP leader Alex Salmond hopes that the report, which is being published almost seven years after Gordon Brown launched the inquiry, will show that Blair committed to the invasion of Iraq in private with President Bush before 2003.

His successor, Sturgeon, said: "The long awaited publication of the Chilcot Report could be a defining moment of truth for Tony Blair, the Labour party and the way government is run in the United Kingdom. The Iraq war was a foreign policy catastrophe that had a devastating impact on many families across the UK, Iraq and internationally.

She added: "The Chilcot inquiry was demanded because people wanted answers. People and families must have confidence that, having waited so long for answers, a full picture is given."

Lord Campbell, who was the Lib Dem foreign affairs spokesman when the Commons voted to invade Iraq, said reported leaks suggested that figures close to Blair, as well as the then Prime Minister, would be heavily criticised in the findings.

He also predicted that the standard of military equipment used, and the way the UK Armed Forces campaign was conducted, would also come in for criticism.. "The impression I get from some of the leaks is that there may be a more sustained and coherent criticism of those apart from Blair who were engaged in political decision making, or who had responsibility for what happened afterwards. I have in my mind the tactics that were used by the army and the quality and standard of the equipment available to our troops. There may also be criticism of tactics used to deal with insurgents."

Campbell expects that a key part of Chilcot will focus on emails and other communications sent between Blair and Bush during both the run-up to and during the conflict. "I think the substance of these exchanges between Tony Blair and George W Bush is likely to show how closely involved Blair was. This could be the case in terms of talking about how the politics were going at home and the general political dialogue between Bush and Blair. We'll have a far greater understanding of the political exchanges between them than ever before once private emails are made more public.

"They will give us a clear understanding of the nature and extent of the commitment from Blair and that everything was subordinate to Blair's decision that the UK would join the US invasion of Iraq, irrespective of public opinion at home. I'd expect exchanges that will demonstrate that not even one million people marching in London against the war was going to divert Blair."

Former Linlithgow Labour MP Tam Dalyell, who was a leading opponent of the war, said the report needed to reveal whether Blair ever questioned the intelligence he received about the case for going to war. Blair, he suggested, "cynically twisted" such intelligence and that the report needed to show whether he went his "own sweet way" and went to war regardless of advice, a move he said was "unforgivable".

He demanded: "I want answers - what was the reaction to the repeated questions I put to Blair and other ministers about whether they were absolutely sure of their intelligence sources? But I think that they cynically had the information and twisted it. That they went their own sweet way, which was unforgivable. I just want the factual answer as to what they did when they were asked about the veracity of their intelligence."

Conservative MP Dominic Grieve, the chair of Westminster's intelligence and security committee, said Chilcot needed to resolve whether parliament was misled about the reason to go to war ahead of the Commons vote in March 2003.

Grieve, the UK's former Attorney General, added: "I hope that it provides satisfactory answers. Clearly it is anticipated as a major political event, but it still very much depends on the thoroughness of the inquiry."

George Galloway was Labour MP for Glasgow Kelvin at the time of the Iraq invasion. He fears Chilcot will let Blair of the hook by criticising a large number of UK government and senior military figures rather than focussing on individuals at the heart of the decision-making process.

Galloway was expelled from the party for remarks he made about the Iraq war. He said: "A series of leaks suggest that the number of people criticised is likely to be very large, say 45 to 55, which implies a lack of focus on the key figures. There's a danger that if it criticises that many people then the blame is spread too thinly."

He believes that a failure to establish the full facts behind the 2003 invasion would "generate outrage" among the public. "If it fails it will be very dangerous to the British establishment in terms of the credibility of the British state. Given that the levels of credibility in our institutions are already at a dangerously low level it could lead to a further radicalising of Muslim youths. For the British state it's significant potential for destabilising.

He does not, however, believe that Chilcot will be a whitewash."The establishment couldn't take the risk." If there was one, he said "there will be outrage and I'll do my best to generate that outrage."