The Prime Minister will warn that a Labour/SNP “coalition of chaos” threatens the future of the UK and will bring job losses, tax rises and bankruptcy to Scotland.
His warning, which will be made on a visit to Scotland, comes hard on the heels of Mr Clegg’s attempt to highlight the dangers of the UK being run by a “coalition of grievance” involving the SNP or Ukip.
Launching the Liberal Democrat manifesto yesterday, the Deputy Prime Minister tried to revive his party’s fortunes by presenting it as a more palatable junior coalition partner than the SNP or Ukip.
The party leader said a healthy number of Lib Dem MPs would prevent a future government “lurching” to the right or left under the influence of Ukip or the SNP.
“Someone is going to hold the balance of power on 8 May and it won’t be David Cameron or Ed Miliband,” said Mr Clegg. “But it could be Nigel Farage. It could be Alex Salmond. Or it could be me and the Liberal Democrats.
“So ask yourself this: Do you want Nigel Farage walking through the door of No10? Do you want Alex Salmond sat at the Cabinet table? Or do you want the Liberal Democrats?
“The Liberal Democrats will add a heart to a Conservative government and we will add a brain to a Labour one.”
A “few hundred votes”, he claimed, could make the difference between a “decent, tolerant and generous” government in the centre-ground and a “coalition of grievance” involving either the Ukip or SNP.
Labour has already ruled out a formal coalition with the SNP, but Nicola Sturgeon has indicated that her party would work with Labour on a vote-by-vote basis.
The attack on the SNP by its rivals will intensify today when the Prime Minister comes to Glasgow to urge last year’s No voters to back the Conservatives when he argues that his party is the only one that believes in a strong UK.
At the launch of the Scottish Conservatives’ manifesto, Mr Cameron will warn that a Labour/SNP Westminster deal would wreck the economic recovery.
The Prime Minister will portray Labour and the SNP as left-wing parties of high taxation whose policies will hurt working people.
He will say: “‘We meet here in Scotland in the middle of a massive political fight. We’ve got Labour and the SNP on opposite sides – slugging it out – but if you take a step back they’re really on the same side. You have a weak Labour party, who want more spending, more borrowing, more debt and more taxes.
“And the people who will prop them up, the SNP – who want even more spending, more borrowing, more debt and more taxes.
“Together, they pose a clear threat to the future of our United Kingdom. A coalition of chaos. The SNP acting as the chain to Labour’s wrecking ball, running right through our economic recovery – and it will be you who pays the price. With jobs losses, massive tax rises and an economy back on the brink of bankruptcy. In short it won’t work for Scotland, but it will hurt for Scotland.”
He will add: “There’s only one party left holding the mantle of a strong United Kingdom and a strong economy. Only one party speaking above these warring tribes and about what actually matters to working people and it’s us, the Conservative Party. And I tell you, we will never do any sort of deal with any party that wants to break up our United Kingdom.”
Last night, the Conservatives attempted to suggest that Labour and the SNP were already working hand in glove at Westminster by producing figures that showed Mr Miliband and the Nationalists voted together 292 times between 2010 and 2015 at Westminster.
Mr Cameron’s hard-hitting speech will reinforce the message sent out by the Chancellor George Osborne when he visited the North-east of Scotland yesterday.
The opinion polls are predicting huge gains for the SNP at the expense of Scottish Labour – a scenario that could see First Minister Nicola Sturgeon’s party propping up an Mr Miliband administration at Westminster.
On a campaign visit to the Lib Dem-held West Aberdeenshire and Kincardine constituency, the Chancellor talked up his party’s Scottish prospects, despite the Conservatives defending just one seat north of the Border.
He said: “We’re choosing a UK government at this election and I think the most important issue is going to be who do you want to have that economic plan that is creating jobs, keeping the United Kingdom strong.
“There’s really only one choice in this election,” he said during a visit to McIntosh Plant Hire near Westhill, Aberdeenshire.
“You either have the Scottish Conservatives, led by Ruth Davidson, who are promising a strong economy, strong defences and strong United Kingdom, and you have the alternative which is this Scottish Nationalist/Ed Miliband cabal which is offering higher taxes, higher debt, a weaker economy, weaker defences.”
The Conservative election manifesto, published earlier this week, was attacked by Labour as a “brutal betrayal” of the cross-party Smith Commission proposals, which include transferring powers over income tax north of the Border to the Scottish Parliament.
Last night SNP depute leader Stewart Hosie said: “It’s getting clearer by the day that the idea of a strong team of SNP MPs holding real power for Scotland at Westminster – and helping deliver progressive politics across the UK – has David Cameron shaking in his boots.”