Labour leadership frontrunner Jim Murphy has pledged to end Labour's losing streak as a poll says the number of MPs in Scotland could be slashed from 41 to four at next year's General Election.

Announcing his candidacy, Mr Murphy said: "I don't care whether you're left-wing or right-wing, New Labour or Old Labour - it's losing Labour I want to get rid of."

The East Renfrewshire MP was speaking before Labour leader Ed Miliband attended a gala dinner organised by the party in Glasgow.

Mr Miliband was barracked by about 200 pro-independence supporters as he arrived. He said he planned to work "shoulder to shoulder" with the new leader, telling colleagues he would fight "with every fibre of my being over these months to show how we can change Scotland ... and change Britain".

But Mr Miliband again stayed silent on former leader Johann Lamont's allegation the Scottish party was "just a branch office" of the UK party in London - a claim Mr Murphy denied.

At the annual event, current interim leader Anas Sarwar MP said he planned to stand down as deputy leader.

The scale of the challenge Mr Murphy, the Shadow International Development Secretary, could face if he is elected became clearer with a new poll. An Ipsos Mori survey of 1,000 people for STV predicted a dramatic fall for Labour and a stunning rise for the SNP, increasing its share of Westminster seats from six to 54 out of Scotland's total of 59.

Mr Murphy made clear he would be firmly in charge if he won the leadership on December 13 and that the Scottish party would be more autonomous and distinctive.

He will officially launch his campaign tomorrow and is expected to resign from the Shadow Cabinet soon. He made clear he wants to "strike a different tone" and concentrate not on shouting at the SNP but on listening to the Scottish people.

The 47-year-old MP stressed that the party had to take much more responsibility for its own decisions.

"Those who know me know I am big enough and ugly enough not to be pushed around ... I am going to unite the Scottish Labour Party. I will decide as Scottish Labour leader who we appoint, how we hire, how we fire and all those sorts of big issues," he added.

Mr Sarwar, speaking of his decision to stand down, said: "I think it is right we have a concurrent leadership and deputy leadership election."

Nominations for the leadership officially open today and close on Tuesday. Voting begins on November 17, with the result declared on December 13.

Other candidates are MSPs Sarah Boyack, the former Holyrood enterprise minister, and Neil Findlay, the party's health spokesman and a left-winger.

Commenting on the survey, John Curtice of ­Strathclyde University noted that if it was the case the Nationalists were experiencing a surge in support for Westminster, then Labour seats "could fall like nine pins". He added: "If there were to be serious losses, then Labour's chances of emerging as the largest party at Westminster would be significantly diminished. The prospects and careers of every single Labour MP depends on whoever is leader of the Scottish Labour Party delivering in Scotland."

The poll found 52 per cent of people questioned in Scotland said they would vote for the SNP. Support for Labour fell to 23 per cent while that for the Tories was 10 per cent and the LibDems and Greens were both on six. In 2010, Labour polled 42 per cent of the Scottish vote, with the SNP on 20.

In terms of Westminster seats, such figures would mean the Nationalists taking 54, Labour four, the LibDems one and the Tories none, according to a forecast by the Electoral Calculus website.

First Minister-elect Nicola Sturgeon said the SNP had the power to send a "shockwave" through Westminster.