NICOLA Sturgeon has been urged not to rush into holding a new independence referendum – and only to told it when she is “certain of victory”.

The intervention has come from SNP MP Pete Wishart, a possible contender in the forthcoming contest for depute party leader, and follows on from suggestions made by MSP James Dornan, the first declared candidate to enter the race, that a new vote should be held as early as next year.

Writing in The National today, Wishart addressed the timing issue and cautioned against proceeding with another vote before 2021 unless there was evidence a Yes vote would be won.

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Wishart said the negative economic impact of Brexit may not become apparent to voters in Scotland until after the EU/UK transition period ends, at the end of 2020.

He believed it was at such a point that support for independence would rise. However, he also left open the possibility of an early vote if circumstances favoured victory.

“In this Parliament we do have a mandate to hold another referendum and if we begin to see evidence that the time is right it should be deployed,” he wrote.

“But we only should hold a referendum when we are certain of winning and not hold one just because we can.

“If the optimum conditions are assessed to be found on the other side of a Scottish election then we should properly prepare and ensure that a mandate is once again forcefully renewed, undisputed and incontrovertible.

“I actually believe that it would be impossible to win a referendum if we can’t secure a mandate to hold one.

“Then there are events. It is not beyond possibility that the UK Brexit project will totally implode in chaos and the ‘optimum’ time comes into play sooner rather than later.

He added: “We should obviously grab that opportunity and quickly put in place a referendum. But with this scenario we’re literally talking about months and is therefore something we cannot properly plan for and would be largely out of our control.”

He concluded by saying Scotland would become an independent country – if former No voters were persuaded to change their minds.

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“Scotland will secure its independence and we are so tantalisingly close, but we have work to do in convincing our fellow Scots who voted No last time to join us as well as uniting all Scots from both sides of the EU referendum. Setting a roadmap and plan is essential in getting us there as is striking at the optimum time for success.” The timescale for the depute contest is due to be set out in early March with the winner announced in June. Dornan, the Glasgow Cathcart MSP, is the only declared candidate to date. He told a Sunday paper a Yes vote could be achieved in 2019 or 2020.