NICOLA Sturgeon should withdraw her plan to use the next general election as a "de facto" referendum and instead build substantial majority support for independence, according to a former deputy leader of the SNP.

Jim Sillars, who initially backed the policy, said he had reconsidered his views since last June, when the First Minister unveiled the proposal in Holyrood.

He told The Herald he now thought it was a "hostage to fortune" which could backfire on the party.

His comments come as the SNP's ruling body the National Executive Committee today gather to discuss the de facto indyref proposal with Ms Sturgeon's ahead of a special party conference in March.

They also follow considerable concerns by other senior figures in the party including the MPs Pete Wishart and Stewart McDonald, both regarded a Sturgeon loyalists.

The Herald:

"The idea of making the 2024 election a de facto referendum is at first sight attractive," said Mr Sillars, a prominent critic of Ms Sturgeon (pictured above).

"But then you have to assess it coolly and objectively. The first thing that has to be understood is that every Westminster general election produces it's own dynamic and no one can forecast what that is going to be and what the issues that will really engage the electorate are going to be.

"And so you could enter on the basis that this is a one issue general election for Scotland and find that the electorate don't agree.... I think what the party needs at the moment is some fundamental rethinking."

He referred to a passage in last year's Supreme Court judgment which noted that the UK Government "at the present time" does not agree to a referendum and said this point implied "it can happen in the future".

READ MORE: Sturgeon to face 'robust discussion' with SNP NEC on de facto vote

UK ministers including Michael Gove and Alister Jack have suggested that when independence is the settled will of the Scottish people they will not stand in the way.

Mr Sillars added the SNP needed to get to the level where independence was the settled will which he believed would be the case if polling showed around 60 per cent or more of Scots backing it.

"We've got to as a party campaign significantly using all our resources to build up towards that 60 per cent, it could be 58 per cent, around that figure," he said.

He said this objective was important for several reasons including first, that majority support for independence was indisputable and the party would get the agreed referendum; that those on the losing side would have good grounds for accepting the result, and not demand a second referendum (as the SNP did on Brexit).

READ MORE: SNP MP: de facto indyref is 'worst possible' option, but only choice

"And thirdly if we are to make independence successful those who have lost the vote have to buy in to the attempt to make Scotland successful and prosperous," he said.

"What you don't want is a minority dissatisfied from day one and wants a reversal, that's why 58 per cent to 60 per cent is so very important in the forward strategic view."

Mr Sillars went onto say Labour would be putting forward its proposals for constitutional change to Scottish voters in a bid to attract "soft" SNP voters.

"Despite my initial attraction, a proper assessment shows [using the general election as a de facto referendum] would be a hostage to fortune and another waste of time," he said.

"But what happens if they don't get a majority of votes? We have two years to build a solid vote for independence so that no Westminster government could deny that it is the settled will."

Asked whether independence would have to be put on hold if the de facto referendum was lost, he said: "I don't see why the independence campaign would have to be shelved because of a tactical misjudgement by the person who happens to be the leader of the SNP.

"[Members] would then have to say to the SNP you have been mislead since the day after the Brexit vote, you've had six wasted years demanding a referendum you could not achieve, you've now had another two wasted years. It's time for a change of leadership."

Asked if Ms Sturgeon would have to stand down if lost: "Yes her policy would be in tatters."

His views on the need to build up support for independence echo those of former SNP top strategist Stephen Noon who last November, the day ahead of the Supreme Court ruling, called for a pause in the demand for a referendum even if the judgement went in the Scottish Government's favour.

He said: "Even if there is a yes [court ruling] tomorrow I would like there to be a bit of a pause and actually design a process which leads up to a referendum where we are actually making a decision based upon what we think the Scottish people are wanting for the future of the country."

Mr Noon continued: "The ideal for me would be getting to a place where you've got a proposal which commands the support of 55, 60 per cent of the people of Scotland, and you then put that to a referendum. As a supporter of Yes, that has to be a process that doesn't shut off independence as an option."

An SNP spokesman said: "Nothing Jim Sillars says can be given any credibility after he called for independence to be 'de-prioritised'."