Scotland will pay a "heavier price" if more Tory MPs are returned to Westminster in June, according to Nicola Sturgeon.

The SNP leader will cast the general election as a straight fight between her own party and the Conservatives north of the border as she addresses the Scottish Trades Union Congress (STUC) in Aviemore today.

Fresh opinion polls conducted since the snap ballot was announced last week show the Tories have the backing of around a third of Scots, with the SNP supported by around 44% of voters.

Ms Sturgeon will tell trade union members: "The election in Scotland is a two-horse race between the SNP and hard-line Tories.

"The Tories have taken an extreme position, demanding an end to any opposition at Westminster if they win the election."

She will tell the STUC that a strengthened Tory government will impose more austerity measures, including welfare cuts, and lead the UK to a so-called hard Brexit, without European single market membership.

"The more Tory MPs there are, the heavier the price Scotland will pay," Ms Sturgeon will say.

"They're already cutting nearly £3 billion from the Scottish budget. They're hitting family incomes hard by cutting and removing child tax credits.

"They want to remove Scotland from the European single market which will cost thousands of jobs.

"They've done all this with a small majority.

"Now they want to crush any opposition. The bigger the Tory majority the more they will think they can do anything to Scotland and get away with it."

The SNP is seeking to hold on to the 56 Westminster seats it won in 2015.

A majority win in Scotland would ''reinforce'' the mandate for a second referendum on independence, Ms Sturgeon has previously said.

Meanwhile the Scottish Conservatives are focusing their campaign on opposing another independence vote.

Murdo Fraser, Tory finance spokesman, said: "This biggest threat to prosperity in Scotland is not from a Conservative government, but from Nicola Sturgeon's obsession with cutting us off from our biggest market, the rest of the UK.

"The choice at this election is very clear, and it is only the Scottish Conservatives that can be trusted to preserve the Union."

Scottish Labour's James Kelly said: "Nicola Sturgeon is attempting to pull the wool over voters' eyes.

"Her only priority on June 8 is finding an excuse for another divisive referendum, not kicking the Tories out of office."