Blair warns SNP win could lead to break-up of United Kingdom

The Prime Minister has launched a pre-emptive strike against the Scottish National Party as he warned that an SNP victory in next year's elections would plunge Britain into a "constitutional nightmare".

He focused his fire on the nationalists days before the SNP attempts to strike a new blow against the Government's stance on Iraq at the end of the Queen's Speech debate on Monday.

More than 100 MPs have signed a joint SNP-Plaid Cymru amendment to the Queen's Speech calling on Mr Blair to come to the Commons with a new strategy for dealing with the Iraq crisis.

The nationalists, who provoked a high-profile vote on Iraq last month, hope to force a Commons vote on the issue to embarrass Mr Blair as part of their campaign to highlight the issue of Iraq ahead of Scottish Parliament elections in May.

The Prime Minister devoted his entire speech to the Scottish Labour conference in Oban yesterday to the threat from the SNP to the Labour-led coalition administration in the Holyrood Parliament.

He denounced the SNP stance over Iraq, saying it was absurd to think that voters would decide the Scottish government on a single issue and lambasted their "obsession" with breaking away from the UK.

Mr Blair said: "If it weren't Iraq, it would be something else - anything else, anything that lets them say the problem with Scotland is England, it's Westminster, it's London."

Mr Blair told the party's rank-and-file activists that the SNP was "deadly serious" about creating an independent Scotland. He said: "Imagine May 2007. The SNP plunge us into a constitutional nightmare. It's not the constitution alone I fear for. It's what it says about us, about the people, about our nations. That at a time of momentous challenge when our path to progress was clear, we lost our nerve and turned in on ourselves ... The same people with the same politics want one last try. Their argument has departed, but their obsession remains.

"And it is sad, because whereas we should be debating the virtues of this or that policy, issue or personality, we are forced to debate again a cause - the Union or separation."

Mr Blair told the conference: "Already they are publishing plans for separation - separate currency, separate pensions and social security systems, leaving Nato. The fact they are saying it and with utter precision shows they are deadly serious and would do it."

Mr Blair added: "Without Labour, Scotland would never have seen the progress we have made these past 10 years.

"Together we did it. Together, from today, we must fight to defend it."

Alex Salmond, the SNP leader, dismissed Mr Blair's challenge. He said: "Blair bashing the SNP is the ultimate act of 'boomerang politics', as it will simply return to haunt him.

"His attacks reinforce our position as the only challengers to Labour next year, and undermines any pretence that Labour in Scotland are capable of standing on their own two feet without interference from London. These desperate attacks are not a substitute for the substance Labour are clearly lacking, and are just another reason why more and more Scots believe that it's time for a change in Scotland, and time for the SNP."