Scottish and Welsh nationalists have promised to redouble their efforts to impeach the prime minister in the next parliament.

SNP leader Alex Salmond and Plaid Cymru Westminster leader Elfyn Llwyd will be campaigning together in Edinburgh and West Lothian on Tuesday, highlighting their plans to hold Tony Blair to account over the run-up to the war in Iraq.

The two parties have a close working relationship in Westminster and supported an attempt by one Plaid MP in the past parliament to evict Blair from office over what they alleged was his misleading of the Commons.

Adam Price's largely symbolic bid failed as it ran out of time before it could be debated by MPs. But the parties are pledging to use their parliamentary force to re-introduce the unusual and historic measure.

They say a larger nationalist force would be better placed to push the impeachment through, presuming Blair wins re-election next month.

Arithmetic

Salmond said: "Tony Blair has lost the trust of the people of Scotland. The electoral arithmetic means the Tories can't beat him south of the border, but Scotland will play a pivotal role in delivering the knock out blow.

"Each and every SNP candidate elected in May will be lined up behind a motion to impeach Tony Blair, so we can hasten his departure as prime minister.

"The last thing Scotland wants is to see Blair breeze back into Downing Street. Our impeachment plan would make sure he was held to account and would see the prime minister tried by parliament for his lies and misconduct in taking us into an illegal war on George Bush's coat tails.

"What will Tony Blair do next if thinks he's got away with it over Iraq? Already on the cards is a new nuclear weapons system for the Clyde, a new nuclear waste dump and internationally it could open the door to a new conflict ­ against Iran ­ in the Middle East.

"Scotland can stop Tony Blair in his tracks, and wipe the smile off his face, but only by voting for the SNP on May 5."