Politicians, civil servants and voters are increasingly thinking Britain will not leave the European Union despite Theresa May’s attempts to form a “very British” Brexit grand coalition with Labour, Sir Vince Cable has said.

Sir Vince, who is on course to become the next Liberal Democrat leader, said “enormous” difficulties will become apparent during exit negotiations which will amount to “Euratom times a hundred”.

Mrs May’s desire to leave the European civil nuclear regulator has been the subject of a row among Tories in recent days, despite previously being treated as a minor issue.

“More and more people, politicians and civil servants (are) saying actually this thing isn’t going to happen and it’s based on several things,” Sir Vince told a Westminster lunch.

“I think the sheer enormous complexity and difficulty, and then something like Euratom… an issue that nobody had thought about, but we’ve got Euratom times a hundred out there and nobody can see a way through that.”

Emmanuel Macron was elected French President earlier this yearEmmanuel Macron was elected French President earlier this year (Etienne Laurent/AP)

The former business secretary said the EU is now in a strengthened political position with the election of Emmanuel Macron as French president, while the UK faces economic troubles with a short term credit bubble ending and “terrible” data from the car manufacturing sector, which is highly reliant on cross-EU supply chains.

He went on: “So when you add all that together you start to ask the question well how can this possibly happen?

“I’m not putting my reputation as Mystic Meg on the line in saying I’m absolutely confident it would happen, but I think the possibility of this just not getting any further is now becoming very real.”

Sir Vince said the Lib Dems are now in a good position to “break through the middle” as Mrs May has “trashed” David Cameron’s decade of modernising the Tories while Mr Corbyn’s policies are “implausible”.

He said his party, which enjoyed modest gains at the general election and now has 12 MPs, is going for more than “marginal gains” of reaching 20 to 25 seats next time, adding: “I’m thinking much more ambitiously.”

Sir Vince Cable with David Cameron when he was Prime MinisterSir Vince Cable with David Cameron when he was Prime Minister (Anthony Devlin/PA)

“Ten years work by David Cameron to detoxify the brand has been trashed by what they (the Tories) are now doing, clinging to power with the DUP,” Sir Vince said.

“And on the other side, I think we all have to admire what Jeremy Corbyn did, he massively out performed everybody’s expectation.”

Meanwhile, Sir Vince said he could answer Mrs May’s call for parliamentary cooperation on certain issues, now that the Tories have lost their House of Commons majority after a disastrous election, but would not prop up her minority Government through a coalition or deal.

“There are particular issues where inevitably you want to work with people in other parties, whoever they are,” he said.

“I can give you a hit list of things. In my constituency and many others, the top issue at the moment is school funding. If there are people in other parties willing to join a coalition to fight for it, well I’m definitely up for that.

“But there is no question whatever of trying to sustain the Government by the back door.”