NICOLA Sturgeon has launched her prospectus on the economy of a currency of an independent Scotland, saying it offers an alternative to post-Brexit decline with Westminster.

However the First Minister was unable to say how long an independent Scotland would take to rejoin the European Union or set up a new Scottish currency.

She said Scotland would swap sterling for its own pound when the "time is right" after a period that was as "short as practicable".

She admitted independence would mean customs checks at the border with England, but her government was still studying the technology she said should ease problems.

The paper did not say whether the overall tax burden would rise or spending would fall in the early years of independence, although Ms Sturgeon said Holyrood would use its new powers to borrow responsibly.

It suggested immigration would increase to boost the working age population, which is otherwise forecast to shrink.

The third part of the Building a New Scotland series said physical checks on goods, plants, animals and foodstuffs would “likely only be undertaken on the two main trunk routes between England and Scotland or at rail freight terminals”.

In practice that means at the A74(M)/M6 at Gretna in the west and the A1 near Berwick-upon-Tweed in the east.

There are 25 road crossings along the 154 kilometres of the Scottish-English border.

Ms Sturgeon published the 108-page document at Bute House an hour after Jeremy Hunt shredded what was left of Liz Truss’s mini-budget. 

She said it was a reflection of the sorry state of Westminster politics that the Prime Minister hadn’t offered her resignation over the shambles.

She said her paper set out plans for a “stronger, fairer, more sustainable economy” for Scotland under independence that “openly and frankly” addressed voters’ questions.

She said it was “glaringly obvious now that the UK does not offer economic strength and stability or financial security”.

She said: “The UK economy is fundamentally on the wrong path and there is no real alternative on offer within the Westminster system.

“The establishment consensus on Brexit - despite the harm it is causing - illustrates that.

“For Scotland, not being independent means we are being dragged down the wrong path too: one people in Scotland did not vote for.

“To build a more stable, sustainable economy - with fairness and human wellbeing at heart - independence is therefore essential.

“That is the fundamental point we make in this paper. Independence is not an abstract argument separate from people’s daily lives.

“It has at its heart the ambition - and crucially, it equips us with the essential tools - to build a fairer, wealthier, greener, happier country.”

Many of the sections of the paper deal in headline aspirations, but fill in little detail, other than to say the specifics will be decided by the government of the day, after negotiations with the UK Government on the terms of separation and division of assets and liabilities.

For instance, it said an independent Scotland would achieve “fiscal sustainability” by setting out clear “fiscal rules”, but those rules are for a future government to decide and announce. 

The First Minister said: “We do confirm that we would set clear fiscal rules to put and keep public finances on a sustainable path.

“We would intend these to align with the broad principles of the European Growth and Stability Pact, which is currently being reformed.”

Ms Sturgeon has said that if the UK Supreme Court rules later this year that Holyrood can hold Indyref2 without Westminster’s consent, it will take place on 19 October next year.

If not, Ms Sturgeon has said she will fight the next election as a “de facto” referendum on independence.

In the 2014 referendum campaign, the SNP’s currency plan - a formal union with sterling - fell apart after then Tory Chancellor George Osborne ruled it out.

The new prospectus says Scotland would initially use sterling informally while new financial institutions, such as a Scottish Central Bank, were set up and established their credibility with the markets. 

Subject to a series of tests, Scotland would then switch to a new Scottish pound “as soon as practicable”.

She acknowledged that meant monetary policy, including interest rates, would continue to be determined by the Bank of England, whose focus would be on the remainder of the UK.

Ms Sturgeon said there was no set timetable for adopting a new currency, other than as soon as possible, and repeatedly refused to put a minimum timeframe on the change.

That meant she was also unable to give a timeframe for rejoining the EU - a central plank of her case for leaving the UK - as applicants must have their own currencies or use the euro.

She said the application process could start before the new currency was introduced, but accepted it would be a matter of years.

Asked if it would be five, ten or twenty years before Scotland rejoined the EU, she said: “I hope it would be shorter than all of that.”

She said it would not be “responsible” to set a timetable for moving to a new currency.

She said: “If you tie yourself into a timescale you end up doing it at a time that’s not optimal.”

The SNP’s Sutainable Growth Commission in 2018 said it would be the bets part of a decade before an independent Scotland was ready to move to a new currency.