JIM Murphy’s election campaign was in disarray last night as he was accused of running scared after turning down an interview with Scotland Tonight to discuss his claim that Scotland would not face cuts under a Labour Government. This claim was yesterday rejected very publicly, in humiliating fashion, by senior members of the Shadow Cabinet.

In scenes that will only reinforce the image of Scottish Labour as a “branch office” of the UK party, Shadow Chancellor Ed Balls and Shadow Business Secretary Chuka Umunna intervened to say that Murphy was wrong.

The row threatened to overshadow what had been regarded as a strong manifesto launch for Labour and Ed Miliband.

Murphy’s bad day started during an interview with Balls on BBC Radio 4’s Today programme. The Shadow Chancellor was asked if Murphy’s comment on Sunday’s leaders' debate about Labour not needing “to make further cuts” was true. Balls replied that it was not, saying: “Yes, there will be cuts outside non-protected areas across all these budgets, that will apply in England and in Scotland.”

Balls later added that the cuts would be, “of course UK-wide” and that he could not “say to Scotland that you’re going to be exempt from spending cuts”.

This statement from Balls was, according to Deputy First Minister John Swinney, “the biggest revelation of the election in Scotland so far”. He added: “This admission from Ed Balls has demolished Labour’s Scottish campaign strategy.”

Murphy argued that there was no difference between what he was claiming and what Balls was saying and that he had always said that savings would need to be made.

Later on in the day, during an interview with BBC Two's Daily Politics, Umunna was asked about Murphy’s claim, and in a frank reply said: “The leader of the Scottish Labour party will not be in charge of the UK budget.

“The leader of the country, the next prime minister, Ed Miliband, will be in charge of the UK budget.”

First Minister Nicola Sturgeon seized on the comments. “The truth is out about Labour spending cuts," she said.

"Jim Murphy’s false claims in the TV debates have been rubbished by his own party bosses at Westminster, who have hung him out to dry.

“Labour would impose swingeing spending cuts on Scotland and the rest of the UK, carrying on with austerity where the Tories left off – that is the core aspect of the manifesto they have published. It sweeps away Jim Murphy’s pretence, and leaves him devoid of any credibility in this campaign.

“Ed Miliband, Ed Balls and Chuka Umunna have just confirmed that Labour in Scotland continue to be no more than a branch office of Westminster Labour. That is why so many voters in Scotland are moving away from Labour and choosing the SNP, and we will continue to work hard to earn people’s trust.”

The SNP leader continued: “The cuts being proposed by Labour, the Tories and LibDems are a huge threat to the public services we all hold dear. That is exactly why we need a big group of SNP MPs in the next House of Commons to achieve real change and an end to austerity – our pledge is to be a strong voice for Scotland, and use our clout to help deliver progressive politics across the UK.”

Scottish Conservative leader Ruth Davidson joined in the criticism of Murphy, saying he had "had the rug pulled from under his feet by a panicking and shambolic party which seems to have given up on Scotland".

Yesterday evening STV political correspondent Claire Stewart tweeted: “@JimForScotland has turned down @ScotlandTonight request for interview to explain cuts confusion”.

Although the Scottish Labour leader avoided the questions last night, he will undoubtably be asked for clarification from the Scottish press pack at a nursery in Cumbernauld this morning.

Scottish Labour will be furious at the undermining of Murphy by the senior politicians, which add to impression it is merely a “branch office” of the UK party.

The argument also gave opponents an excuse to remind Murphy of comments he made in a Guardian interview in 2011, where he said opposing cuts meant that the party risked undermining its aim for “genuine credibility” on the economy.

Murphy told the interviewer: “There is a difference between populism and popularity. Credibility is the bridge away from populism and towards popularity. It is difficult to sustain popularity without genuine credibility.”

Yesterday Murphy was absent from the Labour UK manifesto launch and, unusually, organised his own campaign event in Glenrothes at the same time as Miliband was delivering possibly the most important speech of Labour’s campaign.

The whole episode will undoubtedly remind voters of former Scottish leader

Johann Lamont’s resignation in October last year. In a blistering letter, she warned Miliband that “the Scottish party has to be autonomous and not just a branch office of a party based in London.”

In that letter Lamont warned Scottish Labour was being ruled by dinosaurs in Westminster who had not realised that Scotland had changed. Lamont signed off by saying that Labour was a family and that she hoped the new leader of Scottish Labour would treat that family well.