Ed Balls will promise today that Labour would end austerity in Scotland as a new poll predicted the party was poised to lose 28 seats to the SNP.
The shadow chancellor is due to travel to Glasgow to claim that backing the Nationalists on May 7 would pave the way for a longer public spending squeeze.
The warning will be issued after a new survey of 40 Labour-held seats north of the border last night showed a 19-point swing towards the SNP.
The research by ComRes found 30% of people who voted Labour in these battleground seats 2010 were planning to switch to the Nationalists, while 81% of people who voted Yes in the independence referendum were poised to support the SNP.
In more positive news for Labour, 49% of the same voters would prefer Ed Miliband to be prime minister, far higher than the 29% for David Cameron.
Asked about potential power-sharing deals in the wake of a hung parliament, the poll found 41% wanted no formal agreement, followed by 21% who backed the SNP supporting a minority Labour government, and 21% who supported a formal coalition with Labour.
In an attempt to stem the flow of traditional Labour backers to the Nationalists, Mr Balls will use his speech today to outline three reasons why he believes “a vote for the SNP is a vote for continued Tory austerity”.
He will say: “First, because they have failed to back Labour’s fair tax changes across the UK which means we can have extra investment for the NHS, education and young people.
“Second, because the SNP remains wedded to a fiscal approach for Scotland which rejects the pooling and sharing of resources across the United Kingdom.
“The SNP’s plans for Scotland would mean, according to the independent Institute for Fiscal Studies, £7.6billion of spending cuts and tax rises. This would have a hugely damaging impact on living standards and public services in Scotland.
“And third, because a vote for the SNP means it is more likely David Cameron stays in Downing Street.
“Every vote in this election that might allow the Tories to be the largest party is a vote for Tory austerity to continue.”
SNP campaign director Angus Robertson said: “This latest poll is another welcome indication of the strong backing for the SNP we are seeing in communities across Scotland, as Labour continues to pay the price for working hand in glove with the Tories during the referendum – and for lining up with them at Westminster to vote for George Osborne’s plans for another £30billion of cuts.
“By electing more anti-Tory MPs than Tory MPs we can lock David Cameron out of Downing Street – and put an end to the ideological commitment to austerity which is hurting communities across Scotland and elsewhere in the UK.”