ALEX SALMOND has come under attack after new figures raised questions about his economic case for independence and Spain's Prime Minister cast doubt on Scotland's chances of being fast-tracked into the EU.

The First Minister was accused of concealing the true extent of the country's financial difficulties yesterday, the day after he published the Scottish Government's long-awaited blueprint for leaving the UK.

Meanwhile, Spain's Prime Minister Mariano Rajoy dealt a blow to SNP claims that the usual, lengthy EU membership procedures would not apply to an independent Scotland.

At Westminster David Cameron broke his silence on the White Paper as he attacked the Nationalists' proposals, using Prime Minister's Question Time to claim Scots still faced a "huge set of questions".

Mr Salmond hit back, warning Scots they faced "the severest cuts in political history" if they refused to back independence in next year's referendum.

The backlash followed the ­publication on Tuesday of the SNP's detailed proposals for an independent country.

The 670-page document, Scotland's Future, included plans to increase immigration, cut taxes and offer near-full time childcare in a bid to grow the economy.

But Alistair Darling, the head of the pro-UK Better Together campaign, accused him of "taking us for a ride" after unveiling new figures showing an independent Scotland could start life with a deficit double that forecast in the White Paper.

A Better Together analysis, by former senior civil servant Jim Gallagher, suggested the newly independent state could face a black hole in its finances of £9 billion to £10bn in financial year 2016-17, the year the SNP say the country would formally split from the UK if there is a Yes vote next September.

The White Paper said the country would be between £4.3bn and £5.5bn in the red in 2016-17.

Speaking in Edinburgh, Mr Darling, the former Labour Chancellor, launched a furious attack on the "slapdash, wildly optimistic approach" of the ­independence blueprint.

He said: "Is Alex Salmond taking the people of Scotland seriously? It looks like he taking us for a ride."

According to Better Together's ­analysis by Mr Gallagher, the White Paper's forecast of Scotland's financial position in 2016-17 is based on best-case scenarios for oil revenues, the cost of borrowing and the country's share of UK national debt.

He said "reasonable but less ­optimistic" forecasts for oil, borrowing and debt would overturn the White Paper's claim that Scotland would be in a stronger financial position than the rest of the UK at the point of independence.

Better Together warned that an ­independent Scotland's debt-to-GDP ratio could be 5.2%, based on more cautious forecasts, compared with 3.4% across the UK.

The debt-to-GDP figure is significant because it is the basis for the SNP's claim that Scotland would begin life as an independent country in a relatively strong financial position compared with the rest of the UK.

Mr Darling said: "It's no wonder people are beginning to ask serious questions about whether we can believe the whole basis of this prospectus. You can't just publish the most optimistic figures, bank them and say it's a done deal."

Speaking in Edinburgh, Mr Darling said it was "astonishing" the 670-page White Paper devoted only a page to Scotland's future finances. He also criticised the lack of clear costings in the White Paper for tax cuts and other policies.

He said: "The Scottish Government is misleading people into believing that frankly you can get whatever you want and there would be no cost to it. They're also being highly misleading in saying on a single sheet of paper that this is the financial basis on which you can plan for the next 50 years.

"You would not get away with it if you were launching a manifesto for a five-year parliament, let alone a manifesto for the next two or three hundred years."

He added: "I am very, very angry they're using figures that don't stand 10 minutes' examination. "Normally it takes several days for a budget to disintegrate. This didn't last a night."

A spokesman for Deputy First Minister Nicola Sturgeon, the minister responsible for drawing up the White Paper, said: "Alistair Darling's rattled and feeble response to the White Paper says it all. The No campaign is rapidly running out of ideas and has nothing positive to say.

"Mr Darling needs to take a look at his own grasp of figures before he questions the Scottish Government's.

"We can't believe a word the No campaign say."