Shadow Foreign Secretary, would lose his seat, while Margaret Curran, the Shadow Scottish secretary, and Anas Sarwar, former deputy leader, would also go.

The poll of more than 16,000 voters in Scotland predicted the SNP would take 15 of 16 crucial marginal seats in the country with an overall 25.4 per cent swing.

If replicated on May 7, Labour would lose 35 of its 41 MPs and all but rob Labour leader Ed Miliband of any chance of winning an overall majority.

The Ashcroft poll followed a previous survey by Survation in December which also brought bad news for Labour in Scotland.

The poll, the first to be released since Jim Murphy took over as leader in Scotland , found 48 per cent of Scottish voters were planning to support the SNPin May, compared to 24 per cent for Labour.

Labour and the Tories were united in a grand coalition at Westminster in the Second World War after Winston Churchill, in his first act as prime minister in 1940, invited the leaders of the Labour, Liberal and Conservative parties – Attlee, Sinclair and Chamberlain – to join the government. This administration mobilised Britain for total war.

Responding to Stuart’s comments on a new grand coalition between Labour and the Tories, a Scottish Labour spokesman said: “This will never happen.”