Jeremy Corbyn’s chances of forming a majority Labour Government at the General Election are “close to zero” because the party looks totally incapable of regaining any seats in Scotland, Britain’s foremost polling expert has suggested.

As the Labour leader completed a two-day campaign tour of Scottish seats, Professor Sir John Curtice suggested the polls currently pointed to a Conservative majority and the best Mr Corbyn could hope for was to lead a minority administration in London.

Sir John, who is Professor of Politics at Strathclyde University, said the days when the election result in Scotland was a foregone conclusion in favour of Labour were over.

“No longer,” he declared. “What happens in Scotland is potentially fundamental to Boris Johnson’s chances of winning the election.”

Sir John told a briefing of Westminster-based journalists: "The chances of the Labour Party winning a majority are frankly as close to zero as one can safely say it to be, given they look utterly incapable of regaining anything in Scotland.

“So, the odds are the SNP are going to come better off; the question is: is it closer to 45 or 50?

“Maybe, the number has got down closer to 45; we do need more polling. Even though the Lib Dems might make non-trivial gains south of the border, the SNP will have to be the favourite party to be the third largest party in the House of Commons still,” the leading psephologist explained.

Sir John said the SNP vote in 2017 went down much more heavily among Leave voters than Remain voters while the opposite was true for the Conservatives despite Ruth Davidson’s personal pro-EU view.

“Why is the north-east where the Tories did well? Because that’s the most Eurosceptic part of Scotland,” he noted.

“Basically, the SNP have got around half of the Remain vote in Scotland but only around 25 per cent of the Leave vote, which does mean that it is 25 per cent of only a third[overall]; it’s about a sixth of the SNP vote is coming from the Leave side.”

Sir John explained that at present the opinion polls showed the Tories were around 10 points ahead of Labour, which put them on course to form a majority government.

“But,” he stressed, “given the Tories are likely to lose a fair chunk of seats in Scotland and some to the Lib Dems, the target lead for the Conservative Party is around six or seven points. If it gets below that, the odds are beginning to swing in favour of a hung parliament.”

The academic pointed out that between 66 and 70 per cent of the Conservative vote at the 2017 election was a Leave vote while around two-thirds of the Labour vote was a Remain vote. At present, nine per cent of the Tory vote and six per cent of the Labour one were going to Nigel Farage’s Brexit Party.

“There is no doubt, despite what Nigel Farage insists, the Brexit Party is taking more votes off the Tories than they are off Labour,” he stressed. But he asked: “What’s the evidence Farage can win a seat anywhere in Labour territory?”

Sir John suggested in the key battleground of northern England Leavers were moving to the Tories. “The Labour vote in these areas is a majority Remain vote. Sixty per cent of Labour voters in this part of the world voted Remain.

“The battle in the north of England is as follows: it is not about the Tories having to somehow or another dramatically win over Labour voters that they’ve never got before; they’ve already got them.

“The battle there for these Labour Leave seats is: can the Tories hang on to what they had the last time and will enough Remain Labour voters switch to the Liberal Democrats to allow the Tories to win those seats?”

He pointed out: “The deep, deep irony is that Jeremy Corbyn is meant to be our radical and extremist politician; he is the only compromiser left on the biggest issue facing the country. What an extraordinary position.

“On the central issue most important to voters Labour are the only party on the centre ground. And we know the centre ground of Brexit politics is thinly populated.

“People either want to reverse Brexit or want it to be done; there aren’t many in the middle.”

Sir John noted how the PM wanted Jo Swinson’s party to pick up votes as they would invariably be Labour ones, thus helping the Tories pick off some seats.

“Boris Johnson would love the Lib Dems to go up until they get to about the same share of the vote as the Tories in which case – oh my god. Because once a party that gets a geographical even spread of the vote gets ahead, it starts to scoop up everywhere rather than lose everywhere, so you get a very rapid turnover…

“But he has no control over the Remain vote. The bet the PM is making is that the Remain vote will not coalesce either across the country as a whole or through various forms of tactical voting but over that he has no control.”