JIM Sillars, the former deputy leader of the SNP, has called on the new Holyrood government to bring forward legislation that would allow Tony Blair to face trial over Britain's involvement in the Iraq war.

He said the former prime minister could be tried in the High Court in Edinburgh if the Scottish Parliament were to pass a War Crimes Act.

While acknowledging retrospective legislation would be unorthodox, he insisted the prosecution of leading Nazis after the second world war had set a precedent.

Read more: Alex Salmond's plan to put Tony Blair in the dock hits legal hitch

Mr Sillars set out his case after former SNP leader Alex Salmond signalled his determination to resume efforts to bring Mr Blair to court.

He said the former premier should by tried at the International Criminal Court (ICC) at the Hague.

However, the ICC immediately undermined the proposal, confirming the "crime of aggression" alleged by Mr Salmond did fall fall within its jurisdiction.

HeraldScotland:

In a letter to The Herald, Mr Sillars agreed that Mr Salmond was "proceeding up a legal dead end".

But he said Mr Salmond "should still be able to get his man" if the SNP combined with the Greens to pass special legislation at Holyrood.

He said: "There is nothing to prevent the SNP Government from tabling a War Crimes Act, incorporating the ICC definition of aggression, and making it retrospective to 2001, which would ensure Blair’s planning from then until the Iraq invasion is covered under it.

Read more: Alex Salmond reveals plan to put Tony Blair in the dock over Iraq War

"Retrospective legislation is usually held to be obnoxious, but both in Scotland and England it has been employed to ensure that Nazis found to be sheltering in these islands were not able to escape from justice."

He quotes from the Nurnberg Tribunal, which tried many leading Nazis after 1945 and which declared that initiating a war of aggression was "the supreme international crime".

"As there is no crime of aggression in Scots or English law, Blair seems to be off the hook.

HeraldScotland:

"But fear not, given the SNP and Green majority in the Scottish Parliament Alex should still be able to get his man - in Edinburgh’s High Court," said Mr Sillars.

"Perhaps Alex, frustrated by the limitations imposed upon the ICC, can have a word with Nicola about using the legal powers of the Scottish Parliament to bring Blair to the justice that otherwise he will escape."

As SNP leader Mr Salmond was instrumental in a campaign 10 years ago to have Mr Blair impeached.

He said he wanted to reassemble the cross party group, made up largely of Scottish and Welsh nationalists, that led the effort before the Chilcot inquiry publishes its findings on the decision to go to war in July.

Read more: Alex Salmond's plan to put Tony Blair in the dock hits legal hitch

Mr Salmond said he expected the long-running inquiry to show that Mr Blair made secret commitment to support then-US president George Bush in the invasion long before MPs backed it in 2003 on the basis of intelligence that later proved to be false.

He said the ICC could provide a route for Mr Blair to be tried for the crime of aggression.

HeraldScotland:

An SNP source said: "We have no plans to table legislation of this kind, but Jim Sillars raises some important points regarding Tony Blair's appalling judgement in joining George W Bush's invasion of Iraq, and the grave consequences it has had.

"And Mr Blair must now await the verdict of the court of public opinion once the long-delayed Chilcot report is published."

Scottish Labour declined to comment.