The former prime minister and Lord Prescott, who was deputy leader under Tony Blair, will lead a series of party rallies next week in an effort to shore up the no vote in core areas of central Scotland after a poll suggested nearly a third of Labour voters could back independence on 18 September.
With pressure mounting on his party within the no campaign to prevent a haemorrhage of Labour voters moving to vote yes, Ed Miliband, the Labour leader, told reporters: "All of us feel a huge sense of responsibility in this; it's an incredible time for the UK, for the future of our country and for building social justice in Scotland."
Pollsters have detected a late surge in support for independence as Alex Salmond's government has partly redefined the referendum as a protest vote against the Tories, lifting the yes vote to within three percentage points of a win, according to YouGov and Survation.
Although the same polls suggest 20% of SNP voters will vote no, the scale of Labour's vote in Scotland and its antipathy to the Tories offers the independence campaign a clear opportunity to present the referendum as a chance to rid Scotland of a Conservative government permanently.
Speculation is growing that a poll this weekend will show a significant yes lead for the first time at a crucial point in the campaign, following successful attacks by Salmond on the Tories' record on the NHS in England and overall spending cuts.
Salmond, the SNP leader, staged a triumphant walkabout in central Glasgow with his deputy, Nicola Sturgeon, where they were mobbed by shoppers.
Their walk down the pedestrianised Buchanan Street was marketed to celebrate the 10th anniversary of their leadership partnership, but it rapidly turned into an ad hoc independence rally as dozens of Yes Scotland activists crowded round them.
With Salmond and Sturgeon posing for selfies and taking handshakes in a scrum of passersby, three young women leant out of the second-floor window of a nearby hairdressing salon yelled: "Go on yersel', Nicola", before starting up a chant of "Yes! Yes! Yes!" that resounded from the crowd.
Salmond said the ground was shifting under the Labour leader's feet. "The problem with Ed Miliband is his lack of credibility on these issues," he said. "This is someone who is in bed with David Cameron; he is in a joint alliance with the Tory party, and at Westminster they have pledged to continue Tory austerity policies."
In contrast, Miliband held a brief and tense walkabout in the key area of Blantyre, North Lanarkshire, visiting a handful of homes as he was pursued by several ill-tempered independence supporters after a rally with a few dozen activists and councillors in the town's miners' club.
With lampposts around the club hung with dozens of yes placards, he admitted it was "absolutely true" that many Labour voters saw the referendum as a chance to rid Scotland of the Tories – implying those voters were not confident Labour would win the next election.
But Miliband said that Salmond's track record on social justice was so poor it did not justify their support. He told party activists Salmond's only redistributive policy was a 3p in the pound cut in corporation tax for big business. "That's redistribution from the working people of Scotland to the large companies of Scotland," he said.
Summoning the spirit of Keir Hardie, a founder of the Labour party who was born eight miles from Blantyre, Miliband said his party was intent on "not just abolishing the bedroom tax here in Scotland [but] abolishing the bedroom tax throughout the UK. [We] care about social justice, we care about the poor; we care about the vulnerable in every part of the UK."
Risking schisms within the pro-UK Better Together coalition Labour has forged with the Conservatives and Lib Dems, Miliband made repeated attacks on the Tories, deriding their policies and track record in an effort to reinforce his anti-Tory credentials.
He cited an unguarded comment from the Scottish Tory leader, Ruth Davidson, this week that judging by UK polls David Cameron was not going to win the next general election. Labour would win, he insisted, giving Scotland's voters the chance to defeat the Tories in eight months time.
"The Conservative party has become the ungovernable party. We saw it 20 years ago under John Major over Europe, and we're seeing it again with David Cameron. And we know what happens with ungovernable parties: they're going to lose the election," Miliband told reporters, before boarding Labour's red-and-white battle bus, the Indy Ref Express, for a low-key tour of a local shopping centre to meet voters.
Miliband's visit was soured by the disclosure that Scottish members of the influential RMT transport trade union had very narrowly backed a yes vote, the largest union to do so.
The turnout among the RMT's 9,000 Scottish members was low at 26% and Scottish Labour said the final result saw only a minority 44% of members backing independence; 40% voted no, and 15% wanted the union to remain neutral.
Yes Scotland has attracted several high-profile Labour figures, including the former leader of the Strathclyde region, Sir Charles Gray, and the former Scottish Labour chairman Bob Thomson. But it has not won significant support among trade unions, with only the Prison Officers' Association Scotland and branches of PCS and the CWU backing a yes vote.
Labour said the rival rail union Aslef is among unions backing a no vote, along with the GMB – which refused to stage a full membership ballot on independence, the Communication Workers Union, the shopworkers' union Usdaw and the cross-industry union Community.
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