Tory attempts to paint the SNP as a divisive force that would drain resources from the rest of the UK risks the future of the union, leading politicians and cultural figures said.

SNP deal with Labour would be match made in hell, says David Cameron Read more

The warnings that the Conservatives are “playing with fire” by trying to discredit the idea of a Labour government propped up by the SNP came as they issued a new campaign poster showing Scotland’s former first minister, Alec Salmond, gleefully picking the pocket of a passerby, with the words: “Don’t let the SNP grab your cash.”

A main thrust of the Conservatives’ recent campaigning has been to try to warn voters in England that a Labour government backed by the anti-austerity SNP would be a financial disaster for the UK and mean more cash heading north of the border.

But the tone of the Tory comments about the SNP and attempts to scare people in England about the potential influence that it could be able to wield at Westminster is increasingly seen by pro-union Scots as hugely irresponsible and a danger to the long-term survival of the union.

Liberal Democrat cabinet minster Danny Alexander, who is fighting to save his Scottish seat of Inverness, Nairn, Badenoch and Strathspey from the SNP, told the Observer that he was appalled by the Tory campaign, which he said risked giving the SNP a grievance against England that the nationalists could use to push again for independence.

I think the Tory campaign has been a total disgrace Danny Alexander

“I think the Tory campaign has been a total disgrace,” said Alexander, who was chief secretary to the Treasury during the coalition government. “I think they are deliberately trying to stir up ill-feeling between Scotland and England in a desperate attempt to fend off Ukip, and I think it has long-term consequences. When you stoke tensions, you are playing with fire.”

In the unlikely event that the Tories win a majority on 7 May, the ill-feeling caused by Tory campaign tactics would fuel the cause of independence that the SNP craves. “I think a majority Tory government would be a disaster for the whole of the United Kingdom, because it would lurch this country to the right economically … but it would be a particular disaster in Scotland, because it would give the SNP what they most want – a grievance to nurse for the Scottish parliamentary election in 2016.”

Facebook Twitter Pinterest SNP leader Nicola Sturgeon surrounded by thousands of supporters in Buchanan Street, Glasgow. Photograph: Jeff J Mitchell/Getty Images

Alexander added: “I don’t think Scotland would vote for independence, but what [a Tory government] would do is put the SNP on course to call another referendum as soon as possible, which would be very damaging for the Scottish economy. A Tory government would give the SNP an excuse for another referendum, and right now David Cameron seems to be going out of his way to give them that.”

Why are the Tories so paranoid about the SNP? | David Steel Read more

Writing on Observer.co.uk, former Liberal leader David Steel says: “The truth is that a new Tory government dependent on Ukip sympathisers in their own midst is a greater threat to the unity of the UK than any band of SNP MPs.”

Steel says the Conservatives are not interested in constitutional reform and argues that their intransigence on this, “plus wobbling on membership of the EU, is far more likely to lead to the break-up of the UK”.

Leading Scottish historian Tom Devine told the Observer: “The Tories are playing with fire by becoming involved in an implicit alliance with the SNP which can only further weaken an already fragile union.

“Only panic within their ranks at the prospect of electoral defeat can possibly explain this madness, which already has attracted public condemnation from the arch-unionist and former Thatcherite minister Lord Forsyth.”