Scotland will be on a currency “journey” if it votes to leave the UK, Nicola Sturgeon has said in a TV grilling on the economics of independence.

In a punishing interview with the BBC’s Andrew Neil, the First Minister also admitted voters might not know Scotland’s trading relationship with the rest of the UK until after Indyref2.

She was also challenged over a catalogue of problems in the Scottish NHS, including missed A&E and treatment time targets, record drug deaths and hospital building scandals.

Mr Neil put it to her: “You’ve called for legislation to protect the NHS from Donald Trump. Maybe the NHS needs legislation to protect it from Nicola Sturgeon?”

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She replied: “Obviously I don’t think that’s the case.”

The SNP leader was quizzed at length on her plans for Scotland to create its own currency after independence, subject to six economic tests, which her advisers say could take a decade to meet.

Ms Sturgeon said Scotland could rejoin the EU on a “relatively quick” timescale even if it was using the pound outside the UK monetary union as an interim currency after Brexit.

Mr Neil said: “You’re seriously saying that you would try to join the EU using the currency of a country that is no longer in the EU? Brussels wouldn’t allow that to happen.

Ms Sturgeon said: “Firstly the pound is Scotland’s currency right now. The proposition is that until the conditions were right to establish our own currency, which we’ve said would be our objective, then we would use the pound to do that.

“We would have a discussion with the European Union about the journey an independent Scotland was on in terms of currency, and the accession, if Scotland was already out of the European Union, to the point where we rejoined the European Union.

“You know there is a number of things that would require to be done.”

After Mr Neil said it was “all very uncertain”, Ms Sturgeon did not deny it, but said: “Well look, Scotland faces right now the uncertainty of being ripped out of the European Union against our will.

“It’s not of our making. And we need to plot the best way forward for our country where we are in charge of the decisions that we take.”

Mr Neil asked how an independent Scotland could accumulate the reserves needed to back up its own currency when it would start life with the largest deficit in Europe, with the SNP’s own Growth Commission predicting it would still be around 3% of GDP after a decade.

Ms Sturgeon said: “Because our task is to get our deficit reducing faster. That is principally through growing our economy faster which remaining in the EU or returning to the EU helps us to do…. I think over time of course we would aspire to run a surplus.”

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Ms Sturgeon also rejected the view of the Institute of Fiscal Studies that her Growth Commission’s plans would continue Tory-style “austerity”. She said: “I don’t accept that characterisation. It [the Growth Commission] recommended spending increases above the rate of inflation. It also has some very strong messages about times when growth was lower than desired. The case for spending more in these periods in order to boost the economy and expand the economy.”

If an independent Scotland was in the EU and the rest of the UK had undergone Brexit, it could result in a trade and customs border with England.

Mr Neil asked Ms Sturgeon why she said the trade friction caused by Brexit could cost 80,000 Scottish jobs, but did not accept trade friction with England would cost any jobs, despite the UK market being three times as valuable to Scotland than the EU market.

Despite wanting Indyref2 in late 2020, Ms Sturgeon said the exact degree of trade friction would be unclear until after Brexit was resolved - potentially after her preferred timetable for a new vote.

She said it would be a “priority” to ensure the smooth movement of goods and services, but added: “We don’t yet know what the UK’s final relationship with the EU will be.

“When we have clarity on that we have to understand those implications and we have to set out clearly how we deal with those implications in order to keep trade flowing between Scotland and England which is in our interests and in the interests of the rest of the UK.”

Boris Johnson has said that if he wins a majority in the lection next month, he would finalise a trade deal with the EU by the end of the transition period in December 2020, but experts think it could take many years longer, with a crash-out on WTO terms still possible.

Jeremy Corbyn has promised to secure a new Brexit deal and put it to a referendum within six months, but again experts believe the timetable is optimistic.

Mr Neil ended with Ms Sturgeon’s record on health, including the 12-week treatment time guarantee she had written into law, but which is now being broken for more than a quarter of patients.

Ms Sturgeon said: “It’s not good enough, but all health services are undergoing pressure from increased demand. Scotland is no different there. “What is different in Scotland is the focus we are bringing now to addressing these issues.”

She cited an £850m waiting time improvement plan already underway. Paul Masterton, Scottish Tory candidate for East Renfrewshire, said: “Here goes Nicola Sturgeon again. We had the same vague assurances during the independence referendum.

“Now once again she’s back telling Scots not to worry their heads, it’ll all be all right on the night.

“The reason the First Minister can’t give a timetable on what might happen to Scotland after independence is because the SNP doesn’t know what will happen. Yet still she insists we must have another referendum next year.”

Pamela Nash, of Scotland in Union, said: “These deluded claims are an attempt to mislead voters. EU membership for a separate Scotland would be far from straightforward and the process is likely to be lengthy with no guarantee of success. It would also almost certainly lead to a hard border with England, with massive economic and social consequences.”

Mr Neil’s interview with Mr Corbyn is on BBC1 at 7pm on Tuesday.