THE Tories have given up completely on Scotland, according to Deputy First Minister John Swinney, after David Cameron delivered another vow to Scotland – that a Tory government would conduct an annual review of Scottish devolution to make sure the rest of the UK “did not lose out”.

Cameron promised that a Conservative government would introduce an annual Treasury review under what he called the “Carlisle principle” to ensure that the actions of the devolved administration in Edinburgh did not have detrimental impacts on other parts of the UK in areas like air passenger duty, tax rates, university tuition fees or energy policy.

But Sturgeon warned him: “Let me say this to David Cameron – we will oppose any effort to undermine the Scottish Parliament.”

Swinnney added: “Last week the Tories abandoned the Smith Commission, this week they are attacking the Scottish Parliament,” said Swinney. “When the Scottish Government has balanced the books every year, it is insulting to the parliament to say a UK Government which has run up £1.5 trillion of debt should check our sums.

“This clearly shows why we need a strong team of SNP MPs to speak up for Scotland and to protect the parliament itself.”

Speaking as the SNP launched its manifesto in Edinburgh, the Prime Minister said the prospect of an Ed Miliband government propped up by Nationalists would be a “match made in hell”.

First Minister Nicola Sturgeon said the SNP would resist Cameron’s plan. And Alistair Carmichael, the Liberal Democrat Secretary of State for Scotland, said the Prime Minister was again demonstrating he didn’t “get” devolution.

The SNP’s spectacular surge in the polls since last September’s independence referendum has led to predictions it could seize as many as 56 of Scotland’s 59 seats, leaving it holding the balance of power at Westminster.

With 17 days to go to the May 7 poll and Scotland dominating the campaign, Cameron issued an appeal to former Tory voters – and those who have never previously imagined themselves backing the party – to give him their support to stop the SNP and Labour “wrecking the country”.

Speaking in Crewe, he warned that voters could be “sleepwalking” towards a result that would put government into deadlock and bring economic recovery to a halt.

“Make no mistake, if Labour and the SNP get into power, you are going to see an alliance between a party that wants to spend, borrow and tax more, with a party that wants to spend, borrow and tax even more,” said the Tory leader.

“It might be a match made in heaven for them but it is a match made in hell for the British economy.

“You would see our deficit climbing up again, spending on welfare soaring again, businesses crushed again, jobs lost again. With Labour and the SNP, our economy will head into ruin again. And who will pay? You will pay – in higher taxes.”

Labour said the Tories were “talking up” the threat of the SNP for their own political interests.

But Cameron said the rise in support for the SNP meant the election stakes have “just got much, much higher”.

He said the “fact” that Labour could not form a government after May 7 without the support of the SNP posed three dangers to Britain. They were the end of economic growth; a government “grinding to a halt” amid vote-by-vote negotiations with the SNP; and cancellation of English infrastructure projects.

He said it was his “duty as Prime Minister” to warn that the choice facing voters had “just got far more harrowing”.

“I want everyone to be very clear before they vote that there’s a simple choice,” said Cameron.

“You can vote for the Conservative party which will continue the long-term plan that’s working – or you can put all that at risk.”