INDEPENDENCE was rejected because the SNP failed to put national identity at the heart of their campaign, according to a book about the referendum battle by a former leader of the party.

In a detailed account, Gordon Wilson argues Alex Salmond and the Yes campaign blundered by focusing on unconvincing economic arguments rather than appealing to Scots' sense of nationhood.

Despite angry SNP claims of "scaremongering" by the pro-UK campaign, he also argues the Yes side should have issued stark warnings about the consequences of a No vote - including telling Scots their children and grandchildren would have to emigrate to find work.

Speaking ahead of the book's publication tomorrow, Mr Wilson described the Nationalists' defeat by 55 to 45 per cent in September's vote as "lucky" and "a narrow escape from disaster" in light of the flawed campaign strategy.

Mr Wilson, who led the SNP from 1979 to 1990, makes a series of damning criticisms in Scotland: Battle For Independence.

He claims the gradualist approach to independence taken by Mr Salmond's minority administration from 2007 failed to prepare the ground for a ­referendum fight.

"If independence was the goal then it was essential to raise the profile of Scottish identity and dissipate British identity," he writes.

Mr Wilson reveals how he voiced frustration with the campaign in a letter to Yes Scotland chairman Dennis Canavan, telling the former Labour MP: "You must be fed up with being a punchbag for the No campaign."

In it, he said the Yes campaign was "too coy to assert our nationhood" and that its case had the "emotional content of a calculator".

He urged Mr Canavan to warn Scots that a No vote would lead to "assimilation to England".

He also said voters should be told their children and grandchildren would have to emigrate because "after a No vote, Scotland will have little future".

Mr Wilson's criticisms go further than his contributions during the campaign, when he used Options For Scotland, the think-tank he set up with Jim Sillars, to present an alternative vision of an independent Scotland.

He also restates his opposition to Mr Salmond's proposal for a currency union with the rest of the UK, criticising the SNP for "forsaking" a Scottish currency in 2009.

He traces the mistake back to the 2007/8 banking crisis, which he claims was mishandled by Mr Salmond's administration.

He says the Scottish Government was caught "like a rabbit in the headlights" when it should have made clear an independent Scotland would have bailed out and nationalised the Scottish operations of RBS and HBOS.

Giving his verdict on the First ­Minister, he says "Alex is not perfect", adding that he takes criticism badly and works too closely with a "narrow circle of loyalists", but adds: "Any minor flaws are overwhelmed by strengths - power of communication, his ability to exude confidence and mastery of opponents through charisma and chutzpah.

"Even without the independence referendum - a major achievement - he is undeniably the most dominant and successful leader the party has known."

Mr Wilson said yesterday: "In the book, I trace areas of campaign concern: sensitivity over asserting Scottish identity when there was a default British identity amongst older people; the failure to set out the economic reasons why Scotland needed to be independent, for example the long-term mismanagement of the Scottish economy.

"Then not enough attention was devoted to what would happen if Scotland voted No.

He added: "Napoleon once remarked that he preferred lucky generals to good generals.

"Alex Salmond, good general as he is, certainly was lucky with the final outcome. It was a narrow escape from disaster."

However, he said the result stood as a "major achievement, not a failure" and praised the grassroots Yes movement.

He said: "The community campaigns and energising of the Scottish public were nothing short of miraculous.

"The Unionists may have won, but Yes has arguably won the war.

"The referendum ignited a long constitutional fuse that could blow Westminster apart."

Looking ahead, Mr Wilson said it was not "politically practicable" to hold another referendum until public demand exists.

In the meantime, he says, the SNP must take a "convincing" number of Westminster seats next May and win a second majority at Holyrood in 2016.