Nicola Sturgeon has been warned against holding an independence referendum next year by a former deputy leader of the SNP.
Jim Sillars said Brexit uncertainty would inflict the same “fatal blow” on the Yes campaign that the currency question did in 2014.
The party has been talking up the prospect of a secession vote in 2018 in the wake of Tuesday’s Supreme Court ruling, which paves the way for UK ministers to bypass Holyrood in triggering Article 50.
But Mr Sillars, who was Alex Salmond’s deputy in the early 1990s and a key player in the 2014 campaign, warned that Yes would lose if a second referendum was held alongside Brexit negotiations.
He said: “The UK Government and the EU will be in the middle of negotiations in 2018, therefore we would be having a referendum without knowing the outcome of those negotiations.
“That would be presented in capital letters as uncertainty.
“The one lesson we should have learned from 2014 on the currency was that uncertainty was the fatal blow to the Yes campaign.
“That uncertainty hung around from day one right through to the end.”
An SNP spokesman said: “A Tory hard Brexit outside the single market, which is around eight times bigger than the UK’s alone, threatens to be economically disastrous for Scotland – hitting jobs, investment and household incomes.
“That is why we are determined to protect Scotland’s place in Europe, and are pursuing all options to do so, including independence if it is the best or only way.
“Mr Sillars is right to warn of ‘the level of uncertainty over Brexit’ – but the worst thing to do in the face of that uncertainty would be to sit back and leave our fate in the hands of a right-wing Tory government, which now thinks it can do what it wants to Scotland and get away with it.”