Support for Scottish independence amongst voters from north of the border has doubled since 2000, according to a new poll.

The YouGov/Sunday Times survey found that 44 per cent of Scots want independence, compared with 42 per cent who favour continued rule from Westminster.

SNP leader Alex Salmond has said he intends to hold a referendum on independence if he wins power in next year's Scottish parliamentary elections.

Next year is also the 300th anniversary of the Act of Union.

Some Labour MSPs believe the prime minister's unpopularity has fuelled discontent with powers remaining in Westminster and want him to resign before next May's election.

The poll of 1,200 Scots voters, conducted at the height of the prime minister’s difficulties between Tuesday and Thursday last week, showed the SNP at 29 per cent , just one point behind Labour.

Scottish voters have proved immune to the 'Cameron effect', however, despite the Tory revival in England. The Conservatives are backed by just 14 per cent of voters, below the Liberal Democrats.

If repeated at a Holyrood election, the result would give the nationalists 38 out of 129 seats, enough to form a coalition with the Liberal Democrats, Labour's current governing partners, and the Greens.

Labour would remain the biggest party with 42 seats, down from 50.