Former Prime Minister John Major has warned that a Labour-SNP deal after the General Election would be a "recipe for mayhem."
The last Conservative to lead a majority Tory government will deliver a speech in the Midlands on Tuesday spelling out the dangers to the country of an Ed Miliband government propped up by the SNP.
Major will say that a Labour government reliant on SNP votes in the House of Commons would be subject to a "daily dose of political blackmail". In his first major intervention of the campaign, Major's warning echoes his fight against Labour's proposal for a Scottish parliament in 1997.
During the 1997 General Election campaign, Major argued Tony Blair's devolution plans would risk a breakup of the UK. The former Prime Minister fears a large SNP influence on a minority Labour government would drag Miliband to the left and would risk the UK's economic security.
With a little over two weeks before polling day Major will say:
Labour would be in hock to a party that - slowly but surely - will push them ever further to the left. And who would pay the price for this? We all would. We would all pay for the SNP's ransom in our daily lives - through higher taxes, fewer jobs, and more and more debt.
But Major's intervention is at loggerheads with Tory peer Lord Forsyth, who said the Conservatives were engaging in a "short term and dangerous" game by playing up the SNP's chances of a victory in Scotland. Forsyth, a Thatcherite stalwart, fears the Tory strategy of ramping up English fears of a large SNP presence at Westminster will only serve to alienate Scotland further from the rest of the UK.
Ed Miliband has ruled our a formal coalition with the SNP and said no SNP ministers will serve in a Labour government. However, Labour haven't ruled out a vote by vote arrangement with Nicola Sturgeon's party.
Yesterday the SNP launched its manifesto, pledging to fight for an end to austerity economics and full fiscal autonomy for Scotland. Nicola Sturgeon said her party would embolden a Labour administration to be more progressive and invited Ed Miliband to work with the SNP to keep David Cameron out of Downing Street.