NICOLA Sturgeon’s chief Brexit adviser has warned the impact on Scotland of leaving the European single market could be “catastrophic”.

Professor Sir Anton Muscatelli, principal of the University of Glasgow and chairman of the First Minister’s Standing Council on Europe, also said Scotland could be the part of the UK hardest hit by the impact of Brexit.

“Over the past several months I and many other commentators have warned that membership of the single market is vital to the economic future of Scotland and the UK. The potential implications are, and I use this word carefully, catastrophic,” he wrote yesterday in a daily newspaper.

READ MORE: Boris Johnson's bridge could cost £120 billion, experts warn

“A Brexit shock on economic growth will put further strain on public spending, which means funding for the health service, schools and many other services that we have come to value as a society. Never mind the extra £350 million a week for the NHS, a spurious promise that even the most ardent Leaver would now shy away from.”

Muscatelli’s comments come days after the First Minister launched her new Scotland in Europe paper, which revealed Scotland’s economy will be hit by a £12.7 billion a year blow by 2030 in the event of a hard Brexit. It represents the loss of around £2300 per annum for each person north of the Border and the equivalent of a 8.5 per cent drop in the country’s gross domestic product (GDP).

“Scotland’s Place in Europe (SPIE): People, Jobs and Investment concludes that if the UK withdraws from the single market and customs union the most profound consequences will be felt in Scotland,” he added.

“For those who argue that this is Project Fear revisited, SPIE also considers the benefits that single market membership has delivered and could deliver in future: positive arguments that have, in my view, been unhelpfully absent from the debate.

“For example, exports to the EU and to countries with trading agreements with the bloc are worth £15.9bn to the Scottish economy at present. Future opportunities, particularly in the service sector and in the completion of the digital single market, are also there. It is worth reflecting that services account for about three-quarters of Scotland’s GDP, against less than half when we joined the EU.

“The longer-term potential gain from completing the single market in services could boost our GDP by 2.4 per cent, an additional £3.5bn, or £688 per person — income that would enhance employment prospects and provide resources for our stretched public services.”

He also hit out at Brexiteers’ claims that “taking back control” required the need to curb immigration saying the contribution that migrants make is both substantial and essential.”