NICOLA Sturgeon's economics guru has warned the party not to brush over the downsides and “hard work” of independence as it ramps up talk of another referendum.

Andrew Wilson, who led the SNP’s Growth Commission, said the nationalists had yet to produce “a prospectus that is honest and clear about the transition, timings and trade-offs, as well as positive about its vision”.

He warned his party not to take “the populist low road of the Brexiters” and barge ahead regardless.

Writing in the Financial Times, the former MSP admitted that independence “would not be easy”, but argued it would be worth it in the long run. 

The intervention comes as the SNP talks up the prospect of independence without saying how it would cope with the impact of Brexit or coronavirus on the economy.

Ahead of the 2014 referendum, the SNP Government gave voters 10 months to digest its 650-page White Paper on independence.

However, despite SNP constitution secretary Mike Russell insisting Indyref2 could be held before Christmas, there is no sign of any comparable prospectus.

The economic landscape has changed hugely since the White Paper and the Growth Commission report of 2018.

Although the latter was written in response to Brexit, it was published two and a half years before the details of the UK-EU trade deal were finalised.

READ MORE: Scotland will be independent by 2026 says SNP's top strategist Andrew Wilson

The SNP has yet to say what trade and border arrangements an independent Scotland would have with England if Scotland returned to the EU but England stayed out.

The Growth Commission also predates the arrival of the Covid pandemic and the economic wreckage it has created.

In his article, Mr Wilson said a string of polls showed majority support for leaving the UK, with Nicola Sturgeon’s Government far enjoying greater public trust than Boris Johnson’s.

He said pro-Union campaigners were “struggling to articulate a positive case” for it “in the face of today’s political and economic realities”, and Scots no longer bought into the claim that Scotland was too poor to be independent or that the transition would be too hard.

He went on: “Brexit changed this, both the fact of it and the manner of it. 

“It was a populist campaign without any prospectus or detail on what would happen next and a result which a significant majority of Scots didn’t want. 

“This and the handling of the pandemic have changed many minds.  

“Whether they remain changed and are joined by others will in part depend on the quality and conduct of the pro-independence argument. 

“If the nationalists take the populist low road of the Brexiters, it is unlikely centre-ground Scots will be persuaded. 

“Produce a prospectus that is honest and clear about the transition, timings and trade-offs, as well as positive about its vision of why this matters, and the Yes side could win big when the choice is put.” 

READ MORE: Opinion - What is left of the prospectus for independence after Covid?

Mr Wilson, now a corporate lobbyist with Charlotte Street Partners, said independence would take time to have a significant positive effect on the economy, keeping the pound initially, and so unable to set its own monetary policy.

“On matters of currency and monetary policy there will be no immediate change with independence but an orderly transition over time,” he said. 

On borders, he said Brexit imposed new ones “to Scotland’s east and west”, but they were of the UK’s making.

“How they are functioning will be clear by the time of a future referendum. 

“The trade-off and choices involved will be for Scots to judge.  The choice will come. 

“There is no question that choosing will carry trade-offs and challenges to weigh up, whatever the decision. Independence would be hard work and effort — anything worth having always is. It would not be easy, but more and more Scots believe it is worth it.”

READ MORE: SNP's Andrew Wilson at odds with deputy leader over independence being 'settled will' of Scots

The SNP has said it will go into May's Holyrood election arguing a majority of pro-independence MSPs being elected will constitute a mandate for Indyref2.

Boris Johnson has already refused to give Holyrood the powers it needs to hold a legally watertight referendum, and has said he would so again if asked.

The Prime Minister argues the SNP should be bound by its talk of the 2014 referendum as a 'once in a generation' event, and that the 41-year gap between the 1975 and 2016 referendums on Europe is the example to follow.