THE SNP appears “caught in a political vortex and cannot avoid holding a second referendum on independence at the worst possible time,” one of the party’s former leaders has warned.

Gordon Wilson also claimed there had been “vacuum and drift” on campaign planning, and “unpreparedness” as the party focused on May’s local elections, instead of its core goal.

SNP members “were not children” and urgently wanted answers about the issues which bedevilled the Yes campaign in 2014 such as currency, finance and trade, he said.

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A Eurosceptic, Mr Wilson also criticised the SNP’s “obsession” with Europe, which he said risked making a Yes vote synonymous with a “non-deliverable” return to EU membership.

He said: “At best a pro-EU strategy will minimise the Yes vote and at worst fracture it.”

Speaking ahead of this week's SNP conference in Aberdeen, Mr Wilson urged Angus Robertson to give up leading the party’s Westminster group to focus on leading the next campaign.

Nicola Sturgeon has not yet called a second referendum, however she has said one is “all but inevitable” if the UK government rejects her proposal for a bespoke Scottish Brexit deal.

The First Minister is expected to take a further step toward a referendum, perhaps requesting the temporary power to hold one, when she addresses SNP activists in Aberdeen.

Mr Wilson, who lead the SNP from 1979 to 1990, said he was against a swift referendum on the back of Brexit, but “reluctantly” recognised its “apparent inevitability”.

He said: “The Scottish National party must exercise extreme care if, as it appears, it is caught in a political vortex and cannot avoid holding a second referendum on independence at the worst possible time.

“For many supporters, that is not the only problem. It is the seeming unpreparedness, almost as if the Party hierarchy is giving priority to the local government elections.”

“When are we to be given the answers on the currency, budget and trade? Who is to lead the campaign and how is it to be financed? SNP members will expect to receive a thorough briefing at Conference and assurances that the errors of 2014 are not repeated.

“SNP supporters are not children. They will want to be given full confidence we are ready to win. In short, where Nicola Sturgeon has been forced to concentrate on the processes, the vital aspect will be the campaign itself. Here there is vacuum and drift.

“If preparations are in hand, it is time to give details to the rank and file.”

He went on: “If I was in Nicola’s position, I would ask Angus Robertson to step down temporarily as Westminster party leader and devote all his time and talents as SNP Deputy Leader to mastermind the coming campaign.”

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Mr Wilson added: “The danger exists that the SNP in its obsession with Europe muddies the waters by emphasising that a Yes vote is not just for independence but to remain in the EU.

“In reality, EU membership is non-deliverable, the Party shouldn’t forget that over a third of Yes supporters voted to leave the EU and of the two thirds who voted to remain in the EU a substantial number will vote for the British union.”

A new BMG poll showed only one in four Scots want a referendum before Brexit in 2019.

Scottish Conservative constitution spokesman Adam Tomkins said: “Angus Robertson can't take charge of a campaign that doesn't and shouldn't exist. His constituents would be furious if he dropped their interests at Westminster in exchange for more separation rabble-rousing.

“It shows just how arrogant the SNP is that it’s making plans for a referendum just a quarter of people in Scotland want.”

Labour MSP James Kelly added: “It is quite remarkable to hear a former SNP leader admit that EU membership for an independent Scotland is a fantasy.

“Gordon Wilson has recognised that the SNP’s separation dream would in fact be an economic nightmare, with us outside the UK and Europe.”

An SNP spokesperson said: “We are fully focused on protecting Scotland from the disastrous impact of a hard Tory Brexit, and still await the UK government’s response to the serious compromise proposals put forward to keep Scotland in the European single market.”