The UK Government must choose a different path on Brexit to avoid the “stark, catastrophic and unavoidable economic reality of a cliff edge Brexit” according to the Principal of Glasgow University.

Anton Muscatelli delivered a speech at the University and warned that Theresa May must step back from leaving the single market and ending freedom of movement no matter the political cost.

Professor Muscatelli said that Scotland needed both the single market and immigration for population and economic stability.

The professor chairs the Standing Council on Europe said there are three possible scenarios.

He said there could be the “cliff edge Brexit” of the UK leaving the EU with no deal and instead reverting to World Trade Organisation rules.

He said this is estimated to come at a huge cost to the UK economy, almost 10% of GDP growth by 2030.

He said: “If this is the route the UK is forced to take the economic consequences would be stark, catastrophic and unavoidable.”

The other option he said is a single market Brexit which he believes appears to have been ruled out so far.

Prof Muscatelli added: “While this would involve serious political costs for the UK Government end entail a reinterpretation of their own red lines, it may be the only way the Prime Minister can avoid the UK economy falling over the Brexit cliff edge.”

On immigration he said the vital importance of freedom of movement to Scotland is clear.

He said: “ EU immigration has helped to stabilise our population and add to the country’s economic activity.”