LONDON (Reuters) - Scottish nationalist leader Nicola Sturgeon said an exit poll showing her party winning 58 of Scotland's 59 seats in Britain's national election should be treated with huge caution.

Ms Sturgeon, widely judged to be the star performer of the election campaign even though she was not running for a seat in the London Parliament, was wary of the projection. "I'd treat the exit poll with HUGE caution," the leader of the Scottish National Party (SNP) tweeted. "I'm hoping for a good night but I think 58 seats is unlikely!"

The exit poll showed Prime Minister David Cameron's Conservatives are on course to win the most seats in parliament with 316 seats, which would be just shy of an outright majority. It put the opposition Labour Party on 239.

Scottish nationalists could take nearly every seat in Scotland but be shut out of any role in the British government, according to the exit poll on Thursday.

If confirmed, such an outcome would deny the SNP the kingmaker role it had sought in the House of Commons and kill off the prospect of a leftist alliance with Labour to force Mr Cameron out of office.

But it would dramatically highlight the political divide between England and Scotland, and could bolster Scots to push for a new referendum on independence, having narrowly lost one last year.

The left-of-centre SNP had offered during the campaign to work with Labour in order to shut out the Conservatives and reverse austerity policies. Labour leader Ed Miliband had ruled out a coalition, insisting he could win an outright majority.

The SNP's surge comes just eight months after the independence vote in which Scots narrowly rejected its call to break away from the United Kingdom.

Since then, however, many Scots have become disillusioned with Labour, which has traditionally been strong in Scotland, seeing it as having moved too far away from the left and closer to Conservative thinking. Some in Scotland deride Labour as "Red Tories".

Promises to devolve more power to Scotland have also gone unfulfilled, leading to a sense of betrayal.

Labour is at risk of some embarrassing defeats in Scotland. These could include Mr Douglas Alexander, a Labour party grandee and shadow foreign secretary, who is in danger of losing his seat to 20-year-old university student Mhairi Black.

Labour faces other close battles in Renfrewshire East, where its Scottish leader Jim Murphy is standing, and in Kirkcaldy and Cowdenbeath, once the stronghold of former Labour Prime Minister Gordon Brown.

Ms Sturgeon - described by detractors as "the most dangerous woman in Britain" but whom polls show as the most popular politician in the country - has stressed that this election is not, for the SNP, about independence.

"Even if...the SNP wins every seat in Scotland, that is not a mandate for independence or a second referendum. This election is not about independence," she said on Wednesday.

But her opponents said the SNP's aim was undoubtedly to push for a second referendum. Mr Cameron's Conservatives had described the prospect of Labour and the SNP running Britain as a recipe for chaos and the potential break-up of the UK.

Not all SNP voters are automatically pro-independence, however, and polls show that the sentiment on that issue has not changed much since the referendum.

One factor that could come into play is Mr Cameron's promise to hold a vote by 2017 on whether Britain should leave the European Union, something Ms Sturgeon has said would be against Scotland's wishes.