THE SNP risks helping Unionists wriggle out of independence if it supports a second referendum on Brexit, the party’s former deputy leader has said.

Jim Sillars said if there was a future Yes vote, the SNP would have left it open to challenge by setting a precedent over Europe, gifting Unionists "a back stop strategy".

He accused the SNP leadership of being “blinded by their devotion to Brussels” and asked SNP members to challenge the party hierarchy on the issue.

Mr Sillars, who backed Brexit, made the intervention after two senior SNP figures signalled they were warming to the idea of a vote on the final Brexit deal.

Nicola Sturgeon said in January “the argument for giving people a say on the final outcome may become irresistible”, but has so far studiously avoided endorsing a second Brexit vote.

READ MORE: There is no Brexit power grab, Jim Sillars tells Scottish Secretary

Tens of thousands of people marched in London on Saturday demanding a vote on the deal, something Brexiters see as a device to reverse the decision to Leave.

The day after, SNP Westminster leader Ian Blackford said he had an “open ear to developments on that front”, and the party was not always “diametrically opposed” to it.

Brexit minister Michael Russell also said he was “absolutely not hostile” to a second vote on a future deal if the result in Scotland could be respected, unlike the Remain vote of 2016.

However Mr Sillars, who was deputy to Alex Salmond in the early 1990s, said a second vote on Brexit was potentially lethal to the independence cause.

READ MORE: Alex Neil and Jim Sillars: the SNP must not back a second Brexit referendum

He said: “If that argument is supported by the SNP on Brexit, how would it defend a winning independence referendum against demands for a second one after negotiations?

“The various actions taken by the SNP to sabotage Brexit are a set of precedents for the losing No side if Yes wins here next time: claims the winners lied, legal action, inventing difficulties, whipping up emotions, obstruction, encouraging the other side in negotiations to be difficult, will all mirror the SNP on Brexit.

“Blinded by their devotion to Brussels, more a religious belief than a rational position, the SNP has gifted the Unionists a back stop strategy if they lose next time.

“The question the membership should now ask is: does the SNP leadership think?”

READ MORE: Nicola Sturgeon running "one-person" government, says Jim Sillars

Mr Sillars, an increasingly frequent thorn in Ms Sturgeon’s side, last week wrote to Tory Scottish Secretary David Mundell saying there was no Westminster ‘power grab” over Brexit, contradicting a year of assertions by the First Minister and her cabinet.

An SNP spokesperson said: "The SNP will ensure that Scotland’s voice is heard as the right-wing Tory government at Westminster attacks devolution, and seeks to impose a devastating hard Brexit that will destroy Scottish jobs, and damage the livelihoods and living standards of millions of people across our country."