BREXIT could kill off the lifeblood of Scottish universities by limiting the free movement of scholars and students, a leading Scots academic has claimed.

The warning from Professor Anton Muscatelli, the principal of Glasgow University, comes as the sensitive topic of immigration is set to rise to the top of the EU referendum campaign today with a report claiming the in-flow of people to the UK in 2014-15 cost the British taxpayer almost £17 billion.

And in a separate development, Labour’s John McDonnell will use a keynote speech to “rescue” the In-Out debate from what he will denounce as Conservative fearmongering, which, he will say, has “brought out the worst in Westminster politics”.

Prof Muscatelli, writing in a personal capacity in The Herald, highlights how a range of Europe-wide funding initiatives and benefits have come to Glasgow and other Scottish universities from EU sources. These include almost £90 million, which makes up 13 per cent of total research funding.

The senior academic argues that the free movement of scholars and students is the lifeblood of universities, noting: “Those who argue against EU membership talk about negotiating free trade without the free movement of talented people. This is a dangerous and unattainable chimera.

“In contrast, the free movement of people and ideas are what our universities are fundamentally about,” he adds.

But Tom Harris for Scotland Vote Leave pointed out how it cost Scottish taxpayers £80m per year to fund free tuition for EU students and, while the UK was part of the EU, they had no choice about that.

“If we leave, that money will be saved and universities will be able to charge European students the same fees they do to students from England, Wales and Northern Ireland; we win twice.”

Meantime, research by Migration Watch, the think-tank that campaigns for tighter controls on immigration, estimated the net cost of the UK-born population in 2014-15 to the public purse was almost £88bn – due almost entirely to the state pension - while migrants from the European Economic Area cost £1.2bn and those from outside Europe £15.6bn; a net total of £16.8bn.

Lord Green of Deddington, the Migration Watch chairman, said: "This report shows EU migration, taken as a whole, is not making the positive fiscal contribution that has so often been claimed…It is adding to the rapidly increasing pressures on housing and public services.”

In response, Steven Woolfe, Ukip’s immigration spokesman, noting how the research showed immigration cost Britain £3m a day, said: "We have a ticking time-bomb of costs that our nation will not be able to cope with as our population grows and those who have immigrated to the UK grow older and make further demands on our stretched pensions and health care system."

In his speech to the TUC in London, Mr McDonnell will denounce the Tories’ Project Fear and say the time has come to "drive out the politics of despair". Labour, he will insist, will be offering a “vision of Europe based on hope and solidarity".

His words follow a warning yesterday from George Osborne that Brexit would result in a “one-way ticket to a poorer Britain”; Vote Leave, in response, accused the Chancellor of panicking and “resorting to ever more lurid scare stories".

The shadow chancellor’s message came as the leading credit ratings agency Fitch said Brexit could lead it to downgrade the creditworthiness of a number of other EU countries and No 10 admitted that a vote to leave could mean EU citizens living in Britain losing their right to stay in the UK.

Elsewhere on the stump, Tory MP Boris Johnson dismissed as “hysteria” media coverage of his remarks likening the EU’s desire for a superstate with Adolf Hitler’s failed ambition to dominate Europe.

At an underwear factory in Derbyshire, the former London mayor dismissed the EU as a "badly designed undergarment", adding: "Knickers to all those who talk Britain down."