Labour insist there is plenty of time for them to make up lost ground in Scotland The Scottish National Party's economic plans are "unravelling" and would have a "devastating" impact on Scotland, Labour leader Ed Miliband has warned
The UK party leader said the SNP's support for Scotland having full control of all taxation would leave a £7.6bn "black hole" in its finances.
It comes amid fresh warnings of Labour's prospects in Scotland, as one poll gave the SNP a 24-point lead.
The SNP said Labour were "desperate" and were backing Conservative cuts.
The Labour leadership is seeking to wrest the initiative away from the SNP amid concerns that by winning a huge swathe of seats in Scotland it could rob Mr Miliband of any change of winning a majority at Westminster.
Labour has been trailing the SNP in the polls in Scotland for months but a [Only registered and activated users can see links. ] published on Friday suggested Labour could be on course for its worst result in about 100 years.
The poll put the SNP on 49%, with Labour on 25%, which - if borne out on 7 May - would leave Labour with only a handful of seats.
But speaking in Edinburgh, Mr Miliband insisted that people were "still making up their minds" and he suggested the only way to prevent another Conservative government was to vote Labour.
What is fiscal autonomy?
The SNP wants the Scottish Parliament to have control over all of taxation in Scotland.
For the shared costs of continuing to run the United Kingdom, it would pay Whitehall a portion of the takings - for defence, the Foreign Office, the Treasury and shared regulators such as Ofcom and Ofgem.
Those in favour say such a move would respond to public demand for more powers at Holyrood. They say it would provide the levers of power over economic policy that could help grow the economy faster. That includes targeted business tax breaks.
Those against say that it would leave a large gap in the nation's finances - a £7.6bn shortfall next financial year over and above a share of the deficit that the UK is already running.
Labour has ruled out a coalition with the SNP in the event of a hung Parliament, saying there are "big differences" between the two parties over a range of issues, including the extent of financial powers to be given to Scotland and the renewal of Trident.
Flanked by Scottish Labour leader Jim Murphy and shadow chancellor Ed Balls, Mr Miliband pledged to spend a lot of time between now and 7 May in Scotland, saying the result there would have huge consequences for the rest of the UK.
The SNP has said the Scottish Parliament should have control over all taxation in Scotland, known as full fiscal autonomy, and said this should happen within a year of the general election.
Labour has said this would mean the end of the Barnett formula, the mechanism used to distribute government funds across the different nations of the United Kingdom, and leave a £7.6bn "black hole" in Scotland's finances.
Mr Miliband said the SNP's claims that they would end "Tory austerity" were false and they would actually "extend" it because their plans for fiscal autonomy would cut them off from sources of UK-wide revenue and increase their pension liabilities.
"Today I challenge the SNP and Nicola Sturgeon to say how they would fill this £7.6bn gap," he said. "Which services will be cut? Which taxes will be raised and what cuts will it mean for pensioners in Scotland when they are taken out of the UK pension system?
The SNP say full fiscal autonomy would leave Scotland's destiny in its own hands "The SNP say in this campaign they are proposing no spending reductions but, in fact, they are proposing dramatic reductions in spending. They must now come clean."
The Labour leader said the choice on 7 May was different from that posed in last year's independence referendum and for the SNP to position itself as the chief opponent of austerity was "strange and wrong-headed".
"I will never sell Scotland short by signing up to the SNP's plans," he said. "And I will never sell Britain short by abandoning the pooling and sharing of resources because this benefits all parts of our country."
He added "The gulf [between the parties] is very wide because they have a totally different set of priorities."
Speaking on Friday, SNP leader Nicola Sturgeon said her party would exert its influence at Westminster to "force the alternative to austerity".
"This is desperation on the part of the Labour Party," she said. "Instead of putting forward a positive case of their own, they are resorting to the same fears and smears that they resorted to during the referendum.
"The truth is the only cuts on the horizon for Scotland are the ones that the Tories are proposing and Labour are backing."
The SNP has said it is prepared to support a Labour government on a "vote-by-vote" basis, if Ed Miliband's party wins the greater number of seats in the Commons, but not an overall majority.
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