Support for Scottish independence has collapsed as Alex Salmond prepares to unveil plans for a referendum next year, a new poll has shown.

The YouGov/Daily Telegraph poll found that 57 per cent would vote against independence, with only 29 per cent in favour. 15 per cent were undecided or would not vote.

Since voters were last asked this question by YouGov in October last year, support for independence has fallen two points, while backing for the Union has increased by four points.

Anthony King, professor of government at Essex University, said: "Alex Salmond increasingly resembles a man trying to drag a heavy vehicle out of a ditch. He pulls harder and harder, but the vehicle remains firmly mired in mud.

"The findings show clearly that most Scots regard the idea of a referendum on Scottish independence as an irrelevant bore and that, if any such referendum were held in the near future, it would be overwhelmingly defeated."

Voters are divided over whether a referendum should be held, with 45 per cent agreeing there should be a referendum within the next two or three years "to settle the matter one way or another".

47 per cent said that there should not be a vote "as this would be a distraction from more urgent issues that need tackling".

Salmond hopes to increase the number of SNP MPs from seven to 20 in order to win concessions in a hung parliament but the poll shows support for his party is falling.

Support for the SNP stands at 24 per cent, down from 36 per cent in August 2008. By contrast, support for Labour has increased ten points to 39 per cent since the August 2008 poll.

Support for the Conservatives is unchanged at 18 per cent, while backing for the Liberal Democrats has fallen 11 points to only 12 per cent.