Jim Sillars says SNP may have to be replaced by new independence party

However the extent of this “rot” could require the independence movement “to set up something new, untainted, in its place”, he said.

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Mr Salmond was cleared of 13 sexual assault charges at the High Court in Edinburgh last month, and suggested he had been the victim of a politically-motivated conspiracy.

His backers blame people at the top of the Scottish Government and SNP.

In the forthcoming issue of the Scottish Left Review, Mr Sillars says the book which Mr Salmond is now writing about his case will be like a “volcanic eruption” for the SNP.

Its revelations “will gladden unionist hearts”, and “a tempest of scorn will sweep down on and over on the independence movement”.

However he also predicts the tempest will run its course, and the movement will endure and triumph.

Mr Sillars was deputy to Mr Salmond when he was SNP leader in the 1990s.

He has previously said Mr Salmond shared informatiion about his case with him in advance of the trial which pointed to a conspiracy against him.

Although this was not produced in court for legal reasons - the judge ruled it could lead to the trial straying off course - the former First Minister now intends to make it public in his book.

Mr Sillars said: “The criminal trial of Alex Salmond may be over, but the trial of the SNP both at party and parliamentary level is yet to begin.

“It is unavoidable.

“The book he is writing, with the material he was not allowed to produce at trial, but which has all the authenticity of Scottish government and SNP party documents, will be like a volcano going off underneath some people. Some whose identities I and others know, but cannot name, must tremble at the prospect of what is to come.

“There could be another police investigation, this time not into Alex Salmond.”

Turning to the political consequences, he goes on: “For the rest of us, it is the effect of that coming volcanic eruption on the SNP as a party, as the electoral wing of the independence movement, that matters.

“Not being in the Salmond camp, but in the SNP, and having devoted the major part of my political life to the cause of independence, I see a need for a complete clear-out of the highest levels of the party before it is again fit to lead.

“The cult of personality, the obsessive desire of leaders for complete control of the membership and parliamentarians, the growth of a clique of acolytes, one-person rule - there has been a rot growing at the heart of this organisation for years.”

In the most extraordinary passage in his article, Mr Sillars suggests the 86-year-old SNP may no longer be fit for purpose and have to be replaced.

He wrote: “The independence movement is not just the SNP, but the movement as a whole has much invested in the party as the instrument to achieve democratic success.

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“As the rot is uncovered, the temptation - already being thought of by some - will be to set up something new, untainted, in its place.

“That might need to be done if the damage to come proves fatal. I hope not, because it is not easy to replace and fill the electoral space of a long established organisation.

“I speak from experience of an attempt to do so in the mid- to late 1970s with the Scottish Labour Party.

“It is better to cleanse a sword than to discard it, in the hope of finding another. But if the sword cannot be cleansed enough … well … we shall see.

“There is enormous strength, and ability, in the independence movement.

“Whatever direction is taken, it will eventually succeed.”

Labour MP Ian Murray, the shadow Scottish Secretary, said: “The SNP civil war is a ticking timebomb that puts the interests of Scotland last.

“The nationalists have spent so long trying to divide the people of Scotland, it appears they now want to divide themselves as well.

“When the coronavirus crisis is over, the idea that people in Scotland will want to go back to the business-as-usual politics of constitutional division is laughable.

“As we all seek to deal with the long-term impact of coronavirus, we need to work together to focus on what matters: our NHS; our communities; people’s incomes; and the economy.”

A Scottish Tory spokesman said: “While Scotland struggles to fight a terrifying public health crisis, the SNP is in the grip of a bitter and acrimonious feud among its biggest egos.

“Salmond’s backers have made themselves known from the start - it’s no surprise to see they are now out for what they see as revenge.

“With senior SNP figures now questioning the existence of the party, the SNP is irrevocably split from top to bottom.”

LibDem MSP Alex Cole-Hamilton said: said: “The SNP are clearly plumbing new depths of internal turmoil when their own former deputy leader is suggesting that a new party may be necessary.” The SNP was asked for comment yesterday.