ONE of Nicola Sturgeon’s own financial advisers has poured cold water on SNP plans to commit to a new Scottish currency after independence.

Professor John Kay, who sits on the First Minister’s Standing Council on Europe, said it was “very hard to see large advantages of actually having a distinct currency”.

Although not discounting the idea outright, he also said the viability of a new currency would depend on persuading “people both domestically and internationally” to hold it.

He told Scotland on Sunday: “It would be open to question whether you would want to go through the bother of having your own currency.”

Prof Kay, who advises Ms Sturgeon’s EU council on financial markets, also sat on Alex Salmond’s Council of Economic Advisers.

The currency issue is set to dominate the opening day of this week’s SNP spring conference, with a split between the leadership and grassroots activists.

Ms Sturgeon broadly backs the plan set out by the SNP Growth Commission, which said the first decade after a Yes vote should focus on deficit reduction and spending control.

Only then should the country consider swapping the pound for a new Scottish currency, and only if six tests on the economy, central banking and public opinion were passed.

A leadership motion to conference would commit the party to having a new currency after independence, but critically does not say when, and insists on using the six tests.

However others in the Yes movement want to scrap the tests and adopt a new currency in the first term of an independent parliament to avoid being tied to UK monetary policy.

The issue goes to a vote on Saturday with Inverclyde MP Ronnie Cowan and former MP George Kerevan backing an amendment for a faster, guaranteed switch to a new currency.

Prof Kay called the leadership’s phased approach “entirely sensible.”

He said: “You can only have an independent currency if people would want to hold it - and on day one post-independence why would they want to hold it? You can carry on using sterling unilaterally frankly for as long as you like. That’s a perfectly viable option.

“That doesn’t rule out the option of moving to a separate Scottish currency at some time in the future. But there are two points there.

“One is that it’s very hard to see large advantages of actually having a distinct currency. And secondly, to have a separate currency you have to persuade people both domestically and internationally that you want to hold it.”

He also said Scotland would have “very limited” scope for setting interest rates different to the rest of the UK or the rest of Europe because all their economies were closely linked.

“We live in a complicated, interdependent world,” he added.

Facing a grassroots revolt, Ms Sturgeon wrote a lengthy defence of her position in the National newspaper on Saturday, saying it was “not credible” to move to a new currency without passing the six tests.

She wrote: “To do so would be tantamount to telling people we will press ahead regardless or our state of preparedness, or the state of the economy, or indeed the interests of the country as a whole. That would not be a responsible approach to take and it would undermine rather than enhance the case for a Yes vote.”

Since 1999, all new EU states have been required to commit in principle to the euro, although not all use it.

When asked about an independent Scotland using the euro as a full EU member, the SNP says Scotland could likewise avoid turning a theoretical commitment into reality.

It is therefore easy to see why some Yes supporters fear an SNP commitment to a new Scottish currency could, like the one on the euro, end up as a commitment in name only.

Mr Kerevan said: “The Growth Commission’s six tests could leave Scotland using the pound indefinitely, result in cuts to services and spending, and allow the market to dictate an independent Scotland’s decisions. Sterlingisation and the six tests would effectively negate the very point of seeking independence for Scotland.

“We should not pursue prolonged sterlingisation which would chain Scotland to Westminster which has long made decisions contrary to Scotland’s prosperity and will and leave Scotland without the powers to properly manage our economy - especially during another crash.”

Interim Scottish Tory leader Jackson Carlaw said it was “depressing but not surprising that, ahead of the SNP conference, Nicola Sturgeon is once again focussing on her plans for independence, rather than the key challenges that Scotland faces right now.”