Nicola Sturgeon’s strategy of making the next Westminster general election a de facto referendum will not secure Scotland’s independence, a senior SNP MP has warned.

Stewart McDonald, formerly the party’s defence spokesman in the House of Commons, said the SNP should instead be focusing on driving up support for Scotland leaving the UK, and that “we need to get that campaign fired up now”.

He was speaking as he published a paper which describes a de facto referendum as a “deficient mechanism for the party to opt for”, and which has “the potential for all sorts of problems for the cause”.

SNP veteran and former Scottish Government cabinet secretary Alex Neil, meanwhile, has declared that a de facto referendum “is likely to be an own goal” for independence campaigners.

Their intervention comes ahead of a special SNP conference next month, at which the party will formalise its approach.

The conference was planned after the Supreme Court ruled the Scottish Parliament does not have the power to stage its own referendum without Westminster backing.

Successive Conservative prime ministers have refused requests from Scottish First Minister Ms Sturgeon to stage another ballot on the future of the UK.

In his paper, Mr McDonald, the MP for Glasgow South, said: “A de facto referendum, regardless of whether it takes place in a Westminster or Holyrood election, will not secure Scotland’s independence.”

With a “new, more muscular form of British nationalism” within both the Conservatives and Labour, he said even if the SNP won the vote the UK Government could refuse to open independence negotiations.

He spoke of the “vast asymmetry of power between Edinburgh and London”, and added: “If only one government is treating an election as a de facto referendum, how can a result for independence be implemented?”

Speaking on BBC Radio Scotland’s Good Morning Scotland programme, the SNP MP argued the move for a de facto referendum within the SNP is a “a symbol of our own impatience”.

He added: “The problem I think we need to solve is that at the minute we don’t have majority sustained opinion in favour of independence.”

SNP leader Nicola Sturgeon has made clear her intention to use the next Westminster election as a de facto vote on independence (Jane Barlow/PA)

He said Scotland needs to secure the “power that the Supreme Court made clear that the Scottish Parliament doesn’t have”.

He argued this could be achieved by seeking to drive support for independence higher, and said: “I think part of the reason why we are stuck at the moment… is because support for independence isn’t yet clearly the sustained majority opinion in Scotland.

“I think that is the problem we need to fix with urgency before we go into the next election.

“The UK Government line has been ‘now is not the time’. That suggests that there is a time, and I think we get to that point by driving support for independence higher than it is now.”

Mr McDonald insisted his party should “stick to calls for a legitimate referendum”, saying this is “what the public would expect” and also “what the international community would expect”.

He added: “I think our main job is not to continue in the fashion that we have been, but instead we need to get that campaign fired up now, so we go into the next election with the public at our backs, clearly supporting Scotland’s independence and its future place back into the European Union through a legitimate, lawful referendum.”

Donald Cameron
Scottish Conservative Donald Cameron said Nicola Sturgeon does not get to decide what issues an election is fought on (Fraser Bremner/Scottish Daily Mail/PA)

The SNP should “relish” this, Mr McDonald claimed, saying: “If there’s one thing this party knows how to do it is how to campaign, and I think that is how we can change the mood across the country in favour of independence.”

Mr Neil meanwhile said: “Stewart is correct when he points out that a ‘de facto referendum’ is likely to be an own goal.”

Writing in the A Scotland That Can Vote Yes Paper, the former MSP argued: “The chances of obtaining 50% of the vote in a UK general election are slim indeed.

“Even if we were to repeat the 2015 result when we won 56 of the 59 Scottish seats at Westminster, we would still only get 49.7% of the vote.

“The ‘de facto referendum’ will have been lost. Why hang that noose round our independence necks?”

Scottish Conservative constitution spokesman Donald Cameron said: “Even one of Nicola Sturgeon’s own MPs recognises that her push to turn the next general election into a de facto referendum on independence is completely unworkable in reality.”

Mr Cameron said this shows “this strategy from the First Minister is the height of arrogance and totally irresponsible”.

He added: “It is not up to Nicola Sturgeon and the SNP to tell the public the issues on which a general election will be fought. Voters can decide that for themselves.

“The sooner that Nicola Sturgeon recognises that and listens to not only the wider public, but those in her own party who are clearly opposed to her plans, the better.”