The former deputy leader of the SNP has accused Nicola Sturgeon of misleading independence supporters by “pretending” there will be a second referendum on Scotland leaving the UK this year.

In a letter to the Scottish Daily Mail, Jim Sillars said there is a division within the party between the majority of those who think there will be a vote in 2020 and the minority who do not.

The First Minister is due to give a speech on Friday how she intends to secure Indyref2 despite Boris Johnson’s flat refusal to give Holyrood the powers to hold it.

READ MORE: Nicola Sturgeon to set out 'next steps' on independence on Friday

Senior SNP figures will also attend events and vigils “to mark Scotland’s unwanted exit” from the European Union in the first phase of Brexit at 11pm that night.

However Sillars, who served as deputy leader of the party between 1991 and 1992, criticised those joining marches and rallies in support of independence.

He wrote: "That 45% can march every weekend, while the Unionist majority goes shopping and remains unpersuaded.

"We in the minority know it is those shoppers we need to discuss things with, in a civilised manner, and convert.

"A longer process than a few months; and one that cannot have any worth until we know the final details of the Brexit negotiations."

Sillars also questioned if there was enough "intellectual rigour" in the arguments for another referendum.

He said: "In my political apprentice years, I was taught by old school socialists that the application of intellectual rigour was an essential mental tool when considering policies.

"That quality is sadly missing, if it ever was there, in today's SNP leadership.

"Just a few minutes' study of the idea of an illegal referendum that scrapes past the courts (most unlikely) shows what a nonsense it is.

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"The Unionist majority will take no part, so the SNP ends up with a majority of a minority. What happens then? I have yet to learn of plan B."

An SNP spokeswoman said: “Scotland is due to be dragged out of Europe against its will in a matter of days – in those circumstances we are determined to give the people of Scotland a choice on the country’s future in an independence referendum.

“There is a resounding democratic mandate for a referendum, and the longer that Boris Johnson tries to block it the more that support for a referendum, and for independence, will continue to grow across Scotland.”