First blow to Darling as Yes campaign launched

Mr Darling's initiative makes him the de-facto head of the anti-independence coalition which will fight Mr Salmond's efforts to persuade voters to back his policy in the referendum of autumn 2014.

The study of about 1000 Scottish voters confirms recent research suggesting a lead among those who favour retaining the Union. The poll found 33% wanted independence.

Crucially, the number of swing voters is half the 20% that the SNP believes exists. Dubbed the "persuadables" by Mr Salmond's party, this group is said to be open-minded about independence, but as yet unconvinced.

Mr Darling said the figures proved the First Minister did not speak for Scotland. He added: "At today's launch they'll try and suggest they have the momentum but over five years, indeed for more than 40 years, the numbers on independence haven't really shifted.

"Even after winning two Scottish election victories, raising a war-chest of millions and deploying the full resources of the Scottish Government, Alex Salmond has failed to convince Scots they should leave the UK."

The MP's attack came as Mr Salmond prepares to launch his £2 million pro-independence drive at Cineworld in Edinburgh's Fountainbridge, the area where SNP backer Sir Sean Connery was born.

Sir Sean will not be there, but Hollywood stars Brian Cox and Alan Cumming may attend, while the SNP leader, Green leader Patrick Harvie and former Labour stalwart Dennis Canavan – a convert to independence – will be among the politicians present.

The commissioning of the poll suggests the embryonic No campaign, which does not have an official title, has the financial and organisational clout to compete with Yes Scotland.

Advocate General Lord Wallace also intervened last night, saying it was more important than ever for the two Parliaments to agree a Section 30 order to give the proposed referendum full legal authority.

He said: "Surely we have come too far down this referendum road to run the risk that it could all end up in a legal wrangle with the prospect of no referendum at all. Simply to articulate that possibility underscores the responsibility on the two governments and two parliaments to agree a Section 30 order."

But SNP campaign director Angus Robertson said: "The referendum isn't happening tomorrow, as the poll tried to pretend. Today is the start of the biggest community-based campaign in Scotland's history, offering a positive, inclusive vision of Scotland's future as an independent nation. We are extremely confident of winning the trust of the people."

A source involved in the Yes campaign said research showed the simple concept of "who cares most?" was capable of breaking down opposition to independence, which was often based on single perceptions such as the economy.

"When you push on the question of 'should the people who care most be in charge?' it breaks down the barriers," the source said. "You would want the people who care most about your children to be in charge of their education, for example. This leads to a powerful view that the people who care most about Scotland are the people who live here. That leads to only one conclusion."

Mr Canavan's involvement is significant because around one-third of Labour voters were already in favour of independence while others were capable of embarking on the journey Mr Canavan has made from pro-Union Labour stalwart to supporter of independence.

Former first minister Henry McLeish has warned Labour against being locked into two years of negative campaigning, instead urging the party to embrace a "devo-plus or devo-max" position.

Mr Harvie warned the Yes campaign must quickly develop into a "genuinely cross-party attempt to draw together a compelling and transformational vision of an independent Scotland. Many have concerns about the SNP's middle-of-the-road strategy".