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Ed Miliband has admitted Labour is facing a "big challenge" in Scotland, as one of his MPs warned that the party is in a "dreadful position" north of the border.
Meanwhile, Anas Sarwar, the deputy leader of Scottish Labour, told the party's gala dinner in Glasgow that he will stand down from the post on 13 December.
The announcement means the contests for both leader and deputy leader will run concurrently.
An Ipsos Mori survey for STV today says Labour would poll just 23% of the Scottish vote if an election was held tomorrow.
Piling further pressure on Mr Miliband, Dunfermline and West Fife MP Thomas Docherty today said: "The state that the Labour party is in right now is we are in a dreadful position. And we've got to be honest about ourselves. We have very low esteem with the electorate. The electorate looks at us and has no idea what our polices are."
Speaking to Radio 4's World at One programme, he added: "We have a moribund party in Scotland that seems to think that infighting is more important than campaigning. And we have a membership that is ageing and inactive."
"We can return to be the grown-up party that wants to be in government or we can self-indulge like a throwback to the 1980s and watch our party implode, the SNP win again, the Tories win again, and have another referendum."
But the Shadow International Development Secretary could lose his East Renfrewshire seat if Labour polls just 23% of the Scottish vote, as the survey predicts.
Douglas Alexander and Margaret Curran would also be forced out, according to seat predictor electoralcalculus.co.uk. The site assumes uniform swings across constituencies.
Mr Murphy declared his candidacy this morning and will now join MSPs Neil Findlay and Sarah Boyack in the contest, triggered by the resignation of Johann Lamont.
In an interview announcing her departure, Ms Lamont accused the national party of treating Scotland like a “branch office” but Mr Murphy today promised he would not be dictated to by anyone if he won the leadership.
"The fact is that I’ve been around politics long enough, I am big enough and as your viewers can see, I am ugly enough," he told Sky News.
"I have a thick skin and no one’s going to push me around, on decisions, on tactics, on strategy, on policy, staffing, money, here in Scotland.
"I will try and bring the party together, try and unite the party. These will be decisions made in Scotland, not somewhere else in the United Kingdom."
Mr Murphy confirmed he would be standing for the Scottish Parliament in or before the 2016 Holyrood elections, making him eligible to become first minister if Labour won the most votes.
Meanwhile, Ed Miliband has rejected Ms Lamont's characterisation of the challenges faced by the party north of the border in the wake of the Scots independence referendum.
In an interview with the Daily Record, the Labour Leader said: "I see it differently from the way it’s been described.
“The referendum was led by Scottish Labour with others providing support, like the 100 Labour MPs coming up to campaign. I just see it a different way.
“I came to Parliament after devolution and so I recognise not just the settled nature of the devolution settlement but also the case for further devolution.”
Mr Miliband will tonight attend the Scottish party's annual fundraising dinner in Glasgow.
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