A former SNP leader has warned that the party is caught in a “political vortex” and Nicola Sturgeon cannot avoid calling a second independence referendum “at the worst possible time”.

Gordon Wilson said the Nationalists seem unprepared for another vote, with “vacuum and drift” over how a successor to the 2014 Yes Scotland campaign is to be led and financed.

In addition, he said SNP members were “not children” and deserved answers on a separate Scotland’s currency, budget and trade so there would be no repeat of “the errors of 2014”, when the Nationalists’ failure to outline a credible economic case was blamed for their defeat.

Speaking ahead of next week’s SNP conference, when Ms Sturgeon is expected to make a major announcement about a second referendum, he called for her deputy Angus Robertson to step down as Westminster leader to focus full-time on the campaign.