In this story:

• 'Devolution' backfiring?
• 'Have some guts and stand up'
• Related stories and sites

EDINBURGH, Scotland (CNN) -- Trying to stop an embarrassing political slide that threatens Great Britain's unity, Prime Minister Tony Blair made a whistle-stop tour of Scotland on Friday to personally confront a rising tide of Scottish separatism.

In a speech to Labour Party candidates for the new Scottish parliament, Blair said, "The best future for Scotland is one where the Scottish parliament is used to improve the lives of Scottish people -- not one where it is nothing more than a weapon to tear our country apart.

"So our pledge is a partnership for good -- Scotland strong in a strong United Kingdom," he said.

'Devolution' backfiring?

In last May's national election, Labour -- traditionally strong in Scotland -- came out in support of giving Scotland its own parliament to govern its internal affairs, part of a plan of "devolution," or decentralizing London's control over decision-making in other parts of Britain.

But despite fulfilling that election pledge, and despite the fact that Labour draws strong support in the rest of Great Britain, Blair and his party have watched their support slump in Scotland.

At the same time, polls show that support for the Scottish Nationalist Party -- which supports outright independence for Scotland from Britain -- has soared.

Some polls place the SNP a full 14 percentage points ahead of Labour. If that lead were to hold up, the SNP could snatch an outright majority in the new 129-seat parliament when elections are held next May.

SNP leaders have said if that happens, they will insist on a referendum within four years to break Scotland's nearly 300-year-old political union with England and Wales.

That would be a political disaster for Blair and Labour, who billed devolution as a way to stem support for independence, not facilitate it.

The Labour party's troubles in Scotland stem from an embarrassing string of corruption scandals in local government councils run by the party. It also has been wracked with internal dissension, particularly complaints that procedures used to select candidates for the Scottish parliament were designed to favor moderate Blair loyalists over more left-wing candidates.

'Have some guts and stand up'

In an interview with the BBC, a left-wing Scottish Labour member of the British parliament, Dennis Canavan, said his party's poor standing in Scotland could be reversed if Labor candidates "have some guts and stand up at times and say that the London [Labour] leadership are not getting it right."

In his Edinburgh speech, Blair tried to rally the candidates, optimistically predicting that Labour will "win the argument with the SNP over constructive devolution within the United Kingdom, rather than separatism, which would tear Scotland out of the United Kingdom."

The prime minister warned Scots that if they break away from the rest of Britain, the government would have to raise taxes to survive. Blair also predicted an exodus of business investment from Scotland because firms could not rely on its economic stability.

Candidates said their spirits had been lifted by Blair's visit.

"We are cranking up our campaign now. I think the SNP have peaked too soon. There is a long way to go, and our campaign has been boosted," said Ian McCalman, standing for a Glasgow-area seat in the new parliament.

Reuters contributed to this report.