Hardline “fanatical” Tory Brexiteers are putting their desire to leave the European Union ahead of the national interest and could bring down the Government, Sir John Major has warned.

The former prime minister said Theresa May was facing a battle against “Tea Party” Tories which was tougher than the fight he had with Eurosceptics in the 1990s.

Sir John, who campaigned to remain in the European Union, said if Parliament rejected any deal the Prime Minister struck with Brussels it could force another general election.

He also said there was “undoubtedly” a case for a second referendum on Brexit.

Sir John told ITV News: “I think there are some people in the Conservative Party now who are more dedicated to their concerns about getting the UK out of Europe than they are dedicated to what the implications of that may be for their constituents, or other people’s constituents or the future of our country or the interests of our country or the interests of our party.

“There are more of them now than there were in the 1990s.”

He compared some of the European Research Group of Tory Brexiteers led by Jacob Rees-Mogg to the right-wing “Tea Party” tendency in the US.

“There is a bit of a Tea Party grouping within the hardline European Research Group and that makes it very difficult to negotiate with them.

Jacob Rees-Mogg, leader of the European Research Group of Tories which was criticised by Sir John Major (Stefan Rousseau/PA)
Jacob Rees-Mogg, leader of the European Research Group of Tories which was criticised by Sir John Major (Stefan Rousseau/PA)

“It must be very hard for the Prime Minister to take rather threatening lectures day after day about what they will accept when they are actually a minority in the Conservative parliamentary party.”

He said the splits in the Tory Party could allow Jeremy Corbyn to enter Downing Street.

“I think what they are doing is going to risk a Corbyn government,” he said.

“I think what they are doing is quite likely to lead to a much earlier general election than anybody is anticipating.

“Whether that’s this autumn or next spring I can’t say but I think the way they are continually chipping away against the unity of the Government and you have people in Government who we are told, through the media, are thinking about whether they should resign or not.”

He added that it was an “intolerable position for any prime minister to be in”.

Sir John said: “My concerns are about those people who are a touch too fanatical about the issue, and are really prepared to go to almost any lengths to ensure that we leave Europe, irrespective of the cost to the country, irrespective of the cost to individuals, irrespective of the cost to the Prime Minister, irrespective of the cost to the party, irrespective of anything but their own fanatical determination to make sure we actually leave Europe.

“I’m not sure how you bring those people back into the fold.”