Panicking "Better Together" campaigners are turning to former prime minister Gordon Brown in a frantic bid to win the emotional debate over Scotland's future and stem the flood of Labour voters threatening to hand victory to the nationalists.

With just 10 days to go to the referendum, the possibility of a "yes" vote has sparked bitter criticism of the anti-independence campaign with both its leader, Labour's Alistair Darling, and the prime minister and Tory party under concerted fire.

Former first minister Henry McLeish echoed the widespread view that the "no" campaign had been negative and lacked passion amid the belief too many in Westminster had never accepted the possibility that Alex Salmond could win.

Alex Salmond Gordon Brown
Gordon Brown will take on Salmond in final days Getty

One attempt to counter the negativity will come from Brown with a series of speeches putting his "positive and patriotic" case for a New Union with much greater powers for a devolved Scotland over issues including tax and welfare.

He has previously set out what he believes is his passionate case for the Union but will be pushed further to the forefront of the "no" campaign as polling day approaches.

His influence is seen as crucial because much of the boost to the nationalists has come from traditional Labour voters who, in their disillusion with the establishment, see little difference between the two big Westminster parties.

Brown is still seen as a hugely significant and influential figure in Scotland and will attempt to persuade Labour supporters the nationalists would continue Tory policies.

But David Cameron and George Osborne are also directly in the firing line with some Tory MPs fuming that they have done too little to boost the Unionist campaign and may well preside over the historic breakup of the UK.

The prime minister has a personal dilemma here. He knows that the Tory brand is toxic in Scotland and, thanks to his own background, he is seen as a negative influence in the Better Together campaign.

But, equally, his apparent reluctance to fully engage with the fight has frustrated many in his own party whose fears were summed up by Boris Johnson who warned the country was in danger of "sleepwalking" into separation.

Cameron paid the traditional prime ministerial visit to the Queen in Balmoral at the weekend but made no public appearance and is expected to keep away from the campaign this week.

His spokesman would only confirm that the prime minister "will be in Scotland ahead of the referendum," and denied suggestions he had cancelled a visit for fear of making matters even worse.

David Cameron
David Cameron is seen as toxic Reuters

It also appears no cabinet ministers are currently planning to campaign in Scotland this week. Although the current "headless chicken mode" could yet change that.

Chancellor George Osborne was also under attack for suggesting at the weekend that an announcement was imminent setting out on what more powers Scotland would get after a "no" vote – the so-called Devo Max or best-of-both-worlds option.

It was later stressed the extra powers had been set out long ago and all the chancellor was referring to was a cross-party announcement on the timetabling of the move. That was itself seen as a panic reaction to the latest polls.

It is also suggested the publication of the "plan of action" might be launched by all three Westminster party leaders sharing the same platform.

The obvious danger is that it might only confirm the view in Scotland that the leaders are all part of the same establishment they wish to rid themselves of.

What this all adds up to is a genuine crisis in the Better Together campaign who, despite Darling rightly pointing out he had always warned the gap would narrow, are starting to fear they may have already lost the game.