How Blair may face both criminal and civil actions

Other lawyers have said there are arguments to take the matter to judicial review, which would provide an audit of the legality of the decision to invade Iraq, with a view to criminal charges.

Some have said Mr Blair’s behaviour could amount to the criminal offence of misconduct in public office and have also raised the question of the families taking out a private prosecution.

Lawyers acting for the families of some of the 179 British military personnel killed in the 2003 war are poring over the 2.6 million word report to formulate a civil law suit over allegations the former prime minister abused his power to wage war in Iraq.

Around 30 families of dead soldiers, have asked the law firm McCue & Partners to pursue a claim against Mr Blair. Others are expected to come on board.

The firm is looking at a civil case of misfeasance in public office.

Some legal experts believe families of Iraqis who died in the war could also join the action.

Rose Gentle, from Pollok, Glasgow, whose son Gordon was killed in Iraq, is part of the proposed civil action, but believes that Mr Blair should also face criminal proceedings.

She said: "I think he should be held responsible for what happened. I always wanted it to start, but because it was only to be lessons learned, we had to go with [Chilcot] first. The report gives us something to work on now."

Dr Shavana Musa, a lecturer in constitutional and international law at the University of Manchester believed Chilcot could pave the way for 'victims of families to proceed with criminal and/or civil legal action.

She says Blair could be tried in England and Wales over a charge of 'misconduct in public office', an ancient common law offence, created by judges, which can be traced back to the 13th century.

For the charge to be pursued a public official has to create an abuse of the public's trust in his office, without having a reasonable excuse or justification.

She said: "Under this offence, it could be argued that Blair wilfully misconducted himself amounting to an abuse of the public’s trust in him and did so without any reasonable excuse or justification. A defence for this could be that he received authorisation from the government, which was the 'reasonable excuse or justification' as per the offence.

"It could be said that evidence showing there was no imminent threat from Saddam Hussein was deliberately 'skewed' in order to then ultimately go to war."

Sabah al-Mukhtar, an Iraqi-born lawyer. and president of the Arab Lawyers Association believes Chilcot evidence has uncovered a 'crime of aggression' as there was no threat to the UK to warrant the invasion and he believes criminal charges should be forthcoming.

"Had this happened anywhere else in the world, the people who had taken this decision, where the result of it is as damning as that, would have at least faced charges."

He believed that while Chilcot said the legal basis for UK military action was “far from satisfactory,” and did not rule on its legality, a judicial inquiry could establish what charges could be brought.

"The remit of Chilcot was not to point fingers, not to accuse people, and not to treat people as suspects," he said. "A judicial inquiry would find what they have done is wrong."

Iain Scobbie, a University of Edinburgh law graduate, who has become a leading British expert in international law said there appear to be no routes to prosecute over 'crime of aggression' under Scots or English law.

The former First Minister Alex Samond had previously revealed he wanted Mr Blair to face an investigation by the International Criminal Court if the Chilcot inquiry finds that he made a commitment to US president George Bush to support the invasion.

It had been believed a door could be open for a criminal investigation with the ICC under the offence of "crime of aggression".

But the ICC said that the crime of aggression is “currently not within the ICC jurisdiction, so no preliminary examination can be conducted based on this specific crime”.

The ICC may, in future, exercise jurisdiction over the crime of aggression. A decision on the matter is due to be made by its members after January 1 next year, but it is not thought that any cases could be taken up retrospectively.

The ICC is currently looking into Britain’s conduct during the conflict, but not whether the decision to engage in armed conflict was legal.

However, it has emerged that ICC prosecutor Fatou Bensouda has not ruled out investigating Blair for war crimes.

She confirmed the Chilcot report forms "part of its due diligence" of assessing all relevant material that could provide further context to the allegations of war crimes by British troops in Iraq.

Barrister Martin Browne, who has advised governments on the jurisdiction of the ICC said the possibility of senior political leaders such as Blair, then defence secretary Geoff Hoon and then foreign secretary Jack Straw being charged with offences while possible, was also "negligible".

The ICC is seen as a court of last resort, intervening only when national authorities cannot or will not prosecute.

Mr Browne said: "The Prosecutor of the ICC has rightly not ruled out any individual from the scope of her inquiry and in the next 18 months we will see developments in their investigation that may lead to some individuals being charged for some crimes as the UK’s response is laboriously slow and of questionable effectiveness in uncovering systemic abuses of Iraqis."

November 2016 will be the earliest indication of any 'post-Chilcot' effect, when the prosecutor will release her annual review into the Examination into the Situation in Iraq. As of November 2015 the Prosecutor's office were reviewing up to 200 incidents of unlawful killing or mistreatment by British forces.

Mr Browne said: "It is highly unlikely that Blair could be charged with war crimes for individual incidents that occurred on the battlefield, as they would have to prove some element of knowledge, direction, or substantive assistance in the commission on crimes."

Mr Salmond played a major role in a group pushing for the impeachment of Blair, formed in the main by Welsh and Scots nationalist MPs before he became First Minister - and at a time when the SNP were a minor party in Parliament with just three MPs Now the SNP with 54 MPs are the UK’s third biggest party.

Impeachment was a means by which Parliament could prosecute and try individuals, normally holders of public office, for high treason or other crimes and misdemeanours. The first recorded impeachment in Parliament was in 1376 and the last in 1806.

The impeachment group set off a chain of events that led to Blair’s government avoiding a bloody nose on the Iraq war in a House of Commons vote.

A subsequent motion tabled calling for an immediate investigation of the war ended in a narrow defeat by 298 votes to 273 votes - a majority of just 25.

Hywell Williams, part of the original impeachment group raised the question of impeaching Blair just before Chilcot was published.

But a Commons brefing paper states that the process is considered "obsolete" and has been superceded by other forms of accountability, including a judicial review which it says "now provides an effective check on the legality of the actions of public officials and government ministers".

It added: The growth of the doctrine of collective cabinet responsibility, and the use of confidence motions have both contributed to the disuse of impeachments in modern times.