Ed Balls and Jim Murphy
Ed Balls launched the attack against the SNP with just weeks to go before the general electionGetty

Scottish voters cannot trust the SNP on social justice when they go to the polls this May, according to Ed Balls.

The shadow chancellor launched the attack against Nicola Sturgeon's party with just 36 days to go before the general election. Balls also argued that a vote for the nationalist party would be a vote for "continued austerity".

"The truth is the SNP are the extended austerity party," the Labour front bencher said. He added: "You can't trust the SNP on social justice because the spin doesn't match the reality"

The shadow chancellor promised that a Labour government would give Scotland more funding than the SNP.

Balls also warned that a Tory government would mean £1.5bn ($2.2bn) further cuts from block grants to Scotland from Westminster in the next three years.

The comments come as new Scottish Labour leader Jim Murphy faces a big battle against the SNP north of the border.

A poll from ComRes, which questioned 1,000 Scottish voters in 40 Labour-held seats, estimated a 19-point swing to the SNP

The figures mean that Sturgeon's party would end up in control of around 28 seats currently held by Labour.

In addition, the survey found that almost half (49%) of the respondents wanted Ed Miliband to be prime minister rather than David Cameron (29%).

But a big swing to SNP could jeopardise the Labour leader's chances of getting into Number 10 after the 7 May vote.

The rhetoric between Labour and the SNP has heated up after Miliband ruled out a coalition between the two social democratic parties after the election.

But Sturgeon revealed that the SNP could work with Labour under a "confidence and supply" (vote-by-vote) arrangement.

However, the First Minister of Scotland said Labour would have to drop its plan to renew the UK's trident nuclear missile defence system in exchange for support in the House of Commons.