The prime minister has thrown his weight behind Labour's campaign for the elections to the Scottish parliament.

Tony Blair said that the May 1 poll gave Scots a chance to vote for stability under Labour or "isolation" under the SNP.

"This election will be among the most important in Scotland's history because it will determine the path that Scotland takes over the next four years and beyond," he told an audience in Glasgow.

"This will be a choice between two futures - between devolution and divorce, between investment and cuts, between stability and security, and instability and isolation."

Blair also warned that voting SNP could pave the way for "a risky and expensive divorce".

"The single idea that has defined the soul and substance of the SNP has been its commitment to divorce Scotland from Britain, but they are finding it increasingly difficult to reconcile this central idea to the central developments and challenges of the day," he said.

"Leadership is not about trying to conceal the main policy that defines you as a political party.

"It takes more than an attempted makeover to become a credible party of government; it takes ideas, it takes courage and it takes discipline and commitment."

And he warned against allowing the election to be overshadowed by events in the Gulf.

"With momentous international events still unfolding nightly on our television screens, it is possible that people will be distracted from the importance of the choice they face about the future of Scotland in just over two weeks time," said Blair.

"Compared to matters of war and peace, life and death, it might seem to a lot of people like just another election with just another set of politicians asking for their vote.

"But they would be wrong. It is much, much more than that."

His comments came as all parties geared up for the final fortnight of campaigning.

Shadow foreign secretary Michael Ancram was also in Scotland to give his backing to Conservative leader David McLetchie's bid for the Scottish elections.

Meanwhile the SNP has hit back, attacking Labour's record on the Scottish economy.

"Under Jack McConnell, the Scottish economy has shrunk by almost one quarter of a billion pounds in just one year. Manufacturing exports are down 25 per cent and since his party came to power in 1999, we have lost 33,000 manufacturing jobs," said party leader John Swinney.

"The challenge to Jack McConnell is to explain away the instability that comes from being divorced from the economic control we need.

"Jack McConnell has admitted that the economy is in a perilous state, but we can't wait any longer for him to come round to finding the solution.

"His tired old attacks have no place in the debate on our nation's future and simply reveal that he cannot answer the key question of this campaign."

The SNP has also launched a new poster campaign which depicts McConnell as a Jack Russell sitting alongside Blair and a gramophone with the caption "His Master's Voice".