NICOLA Sturgeon has called for new national debate on immigration, warning of long-term harm to public services and the economy if Brexit cuts the flow of EU migrants to Scotland.

The First Minister said she wanted to “change the narrative” on migration, and persuade people it was vital to the national interest given Scotland’s worrying demographic trends.

She admitted it was not an easy subject for politicians, and people's concerns "cannot simply be dismissed".

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But she said that without inward migration Scotland’s recent population growth would go into reverse, creating a double-whammy of fewer working age taxpayers and an increasing elderly population to support.

Ms Sturgeon faces an uphill struggle to sell her message.

The National Centre for Social Research last week reported a majority of Scots want to leave the European single market and restrict immigration for EU citizens after Brexit.

Two-thirds also want Scotland and the UK to have the same immigration regime after Brexit.

Ms Sturgeon’s call came as she published a new Scottish Government analysis warning a hard Brexit could cut Scottish GDP by £12.7bn, or 8.5 per cent, by 2030.

Even a soft Brexit, in which the UK stayed in the single market and accepted freedom of movement and other EU conditions, would cut Scottish GDP by 2.7 per cent, it said.

It offered no upside to Brexit, other than ending EU payments adding 0.3 per cent to GDP.

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Ms Sturgeon said the paper was intended to influence debate ahead of the next phase of Brexit talks on the transition period and future UK-EU trade relations.

It was also aimed at Jeremy Corbyn in the hope he will swing Labour behind single market membership and help force Theresa May to accept it at Westminster.

She said all three scenarios modelled - Norway-style single market membership, a Canada-style free trade agreement believed to be the UK government’s preferred option, and a hard Brexit on World Trade Organisation terms - were worse than staying in the EU.

However retaining single market membership was the “least damaging” approach.

She said: "For the sake of jobs, the economy and the next generation, today we are calling on the UK government to drop its hard Brexit red lines so that Scotland and the UK can stay inside the single market and customs union."

Many arguments in the paper, Scotland’s Place in Europe: People, Jobs and Investment, echo those put forward those in the government’s previous EU paper of December 2016.

However there was a stronger emphasis on migration.

It said: “We are seeking to change the narrative around migration and demonstrate the value it has to Scotland and the UK by detailing evidence of the role EU citizens play in the viability of key sectors of our economy, manufacturing, services and… delivery of public services.”

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It pointed out 78 per cent of the 219,000 EU nationals in Scotland are in work, each contributing an average of £34,000 in GDP and £10,400 in government revenue.

Ms Sturgeon said the continued flow of EU migrants to Scotland, which could be slashed by a hard Brexit, was “essential to our future economic prosperity”.

She said: “Growing our population, and particularly our working age population, is perhaps the greatest national challenge that we face.

“Over the past 15 years, EU migration has helped to turn around the long term decline in Scotland’s population and mitigate the impact of an ageing society. Over the next 25 years, our own projected birth rate will not be sufficient to grow our population.

“In the period to 2041, all of our projected population growth will come from inward migration.

“Without that, our population could go into decline and with it our ability to grow our economy and fund our public services.”

She said that “stark reality” meant she had “a duty to make the case for free movement no matter how difficult that is sometimes perceived to be”.

Her Brexit minister Michael Russell said the paper was “a positive case for migration, determinedly going against the Brexiteers’ refusal to acknowledge the vital impact and contribution of EU citizens in our society. Frankly, Scotland cannot do without it.”

Professor Graeme Roy, director of the Fraser of Allander Institute, said: “EU migrants are a key part of the workforce, particularly at a time when Scotland's working age population is projected to decline. Whilst the Scottish Government is right to highlight the risks of leaving the single market, like it or not Brexit – in one form or another – appears certain to happen.

“Given this, it is imperative the Scottish Government also start to outline their practical plans to help Scottish businesses respond to the challenges and maximise any opportunities.”

The Scottish Tories said the report failed to mention EU migration to Scotland increasing since the Brexit vote, and ignored most Scots wanting a UK-wide position on immigration.

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MSP Adam Tomkins said: “The SNP government has gone completely over-the-top in its scaremongering here. As the nationalists proved with their independence White Paper, their financial forecasts simply cannot be trusted.

“No one’s doubting that Brexit will pose challenges, but it will bring opportunities too.

“That’s why it’s vital the SNP works with the UK Government to achieve the best Brexit deal.”