NICOLA Sturgeon’s failure to be clear about the currency of an independent Scotland is becoming “not just lamentable but laughable”, a former SNP Cabinet Secretary has said.

In a scathing criticism of the SNP leadership, Kenneth MacAskill said the party urgently needed to set out its position “before criticism turns to scorn”.

Writing in the Herald, the former Justice Secretary also admitted the SNP was at its “weakest on domestic issues”, with a policy agenda that was “limited to say the least”.

In the 2014 referendum, the currency proved the Achilles heel of the Yes campaign, with the UK Government ruling out the SNP’s preferred option of sharing the pound.

Former RBS economist and MSP Andrew Wilson is now examining different currency options for an independent Scotland in his role as chair of the SNP’s Growth Commission.

One possibility is a separate Scottish currency pegged to the pound.

However the Commission has yet to report, and despite Ms Sturgeon calling for a second referendum in 2018/19, her position on a future currency remains unknown.

Asked last week what the currency would be, she told the media: “All in good time”.

Mr MacAskill said the Theresa May’s intervention to block a referendum had helped the SNP by keeping the spotlight on the constitution, but the party continued to face problems.

He said: “The SNP is at its strongest on the constitution and weakest on the domestic issues.

“The Brexit Government, by its belligerent response [has] not just bought the SNP time on the referendum that was badly needed, but also given it breathing space on the domestic issues.

“However, the SNP isn’t out the woods yet. Challenges remain; health, education and the economy will return to the fore.

“Moreover, the fundamental issues that lost the first referendum and undermine the case for a second - the currency and the economy - remain.

“Failure to address the currency issue is becoming not just lamentable but laughable. Action needs to be taken before criticism turns to scorn.

“Options exist and have legitimacy. They need spelled out even if a final position isn’t yet adopted. Afterall, Theresa May has bought them time.”

The comments come after a week of confusion on the currency question.

Last Thursday, SNP MP Joanna Cherry struggled to respond when asked about the currency after independence on BBC Question Time, saying merely “watch this space”.

The following day John Swinney, the deputy First Minister and former Finance Secretary, failed six times to identify the currency when pressed in a BBC Radio Scotland interview.

However on Saturday, SNP Treasury spokesman Stewart Hosie said using the pound was “not as strong an option” as it had been in 2014.

Ms Sturgeon also appeared to shift her position on Sunday, saying Scotland might initially share sterling after independence, then switch to a different currency.

“The starting point for consideration is that Scotland would use the pound,” she told Sky.

Tory economy spokesman Dean Lockhart said: “This is a cutting intervention from someone who, not that long ago, was at the heart of the SNP’s separation campaign.

“If even Kenny MacAskill feels the nationalists’ currency plans are laughable, you can imagine what the voters think.

"With so much SNP confusion over a fundamental issue, how can voters be asked to make an informed decision in an independence referendum?”

An SNP spokesman said: "The First Minister has been clear: Scotland’s choice must be informed. We will be frank about not just the implications of Brexit, but the opportunities and challenges of independence too.

"On currency, the starting point for our consideration is that Scotland would use the pound. It’s our currency too.

"Our Growth Commission of economic experts is currently working on a plan for Scotland's economic future. It will finish its work over the next few months and will then inform economic policy going forward."