Breaking:Red Ed blow as Scots turn backs on Labour, with Tories ahead in the polls for the first time since the 1950s

Ed Miliband is being warned a lack of support in Scotland and a surge by the Green Party in England and Wales could cost him the next general election.

Pollsters say Scottish Nationalists are on course to seize as many as 20 seats in Labour’s heartlands north of the border, while the resurgent Greens are joining Ukip in eating into its traditional support across the rest of the country.

Green leader Natalie Bennett said yesterday her party was aiming to outpoll the Liberal Democrats next year and hoped to seize half a dozen Commons seats.

Recent national polls put them on between 5 and 7 per cent, and they beat the Lib Dems in the European elections.

An SNP advance combined with a surge in support for the Greens next year could badly undermine Mr Miliband’s alleged ‘35 per cent strategy’, which would see him win power on a relatively small share of the vote made up of Labour’s core support plus former Lib Dems disillusioned with the coalition.

With speculation swirling about Mr Miliband’s future, one of his rivals for the leadership, shadow health secretary Andy Burnham, was yesterday forced to insist he would not seek to replace him.

He told the BBC’s Andrew Marr programme : ‘I rule it out... No, I am Labour loyalist to my core. I am loyal to the leader, and the leader of our party, Ed Miliband, has said, the NHS will be his big priority going towards this election.

‘I am 100 per cent focused on developing a plan for the NHS that can speak to the country and can win the next election for Labour and make Ed Miliband prime minister.’

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Interview with Andrew Marr: One of Mr Miliband’s rivals for the leadership, shadow health secretary Andy Burnham (right), was yesterday forced to insist he would not seek to replace him

The latest UK-wide polls by YouGov suggest Labour’s position in Scotland is increasingly in crisis, putting them just six points ahead of the Tories on 26 per cent in one, and on just 20 per cent, one point behind the Tories, in another.

It is thought to be the first time since the 1950s that the Conservatives have been ahead of Labour in a Scottish poll, though the results are based on a small sample size with a large margin of error.

Amid growing infighting and disillusionment, two of Labour’s former Scottish First Ministers launched scathing criticisms of the state of the party. Jack McConnell, now Lord McConnell of Glenscorrodale, said the party must rediscover its 'sense of purpose'.

He said the party’s difficulties were ‘very sad for Labour, but more importantly it’s very sad for those we represent’. He added: ‘What is our purpose? Why should people support us? We need policies and ideas that reflect that – and we’re running out of time.’

Miliband happy at keeping Heywood and Middleton seat recently

Attacks: Two of Labour’s former Scottish First Ministers - Jack McConnell (left) and his predecessor Henry McLeish (right) - launched scathing criticisms of the state of the party 

His predecessor Henry McLeish claimed many of Labour’s supporters no longer know ‘what the party stands for’ and it has lost ‘enormous ground’ to the SNP.

Working-class voters: Shadow Scottish secretary, Margaret Curran (pictured), suggested the party was to abandon Tony Blair’s centrist legacy

Mr McLeish criticised Westminster’s approach to the debate over which powers should be handed to Edinburgh following the No vote in last month’s independence referendum as ‘pathetic’ and ‘clumsy’.

Although Scots backed the Union in last month’s vote, the Yes campaign triumphed in Labour’s heartlands of Glasgow, North Lanarkshire and West Dunbartonshire and Mr Miliband was forced to cut short a campaign visit to Edinburgh after being shouted down by protesters.

To the dismay of the dwindling band of Blairite MPs, their champion, shadow international development secretary Jim Murphy, yesterday ruled himself out of standing as Labour’s leader in Scotland after months of flirting the the job.

‘Rather than being involved directly, I’m determined to be a member of Ed Miliband’s cabinet next year,’ he told Sky News’s Murnaghan programme.

Senior figures close to Mr Miliband are now urging Gordon Brown to take over from Johann Lamont, the struggling current leader, to try to stem the catastrophic losses to the SNP.

Yesterday the shadow Scottish secretary, Margaret Curran, suggested the party was to abandon Tony Blair’s centrist legacy and return to ‘socialist principles’ in a desperate bid to win back working-class voters.

Writing in the Scotland on Sunday newspaper, she said: ‘The Labour Party of today is not the Labour Party of a decade ago.

“We have a leader across the UK who has learned the lessons of Iraq and opposed military action in Syria, who refuses to kowtow to vested interests like the banks and the energy companies and who believes that politics is about building a movement of working people to change our country.

What is our purpose? Why should people support us? We need policies and ideas that reflect that - and we’re running out of time 

Jack McConnell, former Scottish First Minister

She continued: ‘We need a response from the Left that responds to the conditions of people’s lives. The socialist principles of equality, redistribution and social justice need to shape our politics as much today as they did when I joined the party.’

Peter Kellner, president of YouGov, says the SNP is on the brink of a major advance and could win as many as 20 extra seats next year, mainly at Labour’s expense.

He said Labour has ‘big problems’ in Scotland after failing to convince many of their traditional supporters to vote against independence.

A surge in membership in recent weeks has seen the SNP overtake the Lib Dems to become the third biggest party in Britain, with 82,000 paid-up supporters.