FILE PHOTO: Vince Cable speaks after being named as the new leader of Britain's Liberal Democrat Party in London, July 20, 2017. REUTERS/Neil Hall

BRIGHTON, England (Reuters) - Hardline Brexit campaigners are forcing the country into an economic mess to enjoy the “erotic spasm” of leaving the European Union, the leader of Britain’s Liberal Democrats will say on Tuesday.

Vince Cable, who has struggled to turn anger over Brexit rows in both Britain’s Conservative and Labour parties into votes for his pro-EU party, will use a conference speech in the English town of Brighton to press his argument for a “people’s vote”, a second referendum on Britain’s departure from the bloc.

He will also take aim at Prime Minister Theresa May, whose Brexit plan is under fire by not only Brexit supporters demanding a clean break with the EU, but also those who want the closest possible ties. While calling it a starting point for a deal, EU official say they cannot accept some trade proposals.

Cable took aim at those Brexit supporters, who are now pressing the prime minister to “chuck Chequers”, named after her country residence where it was agreed, and instead pursue a Canada-style free trade deal or leave without an agreement.

“For the ‘True Believers’ – the fundamentalists – the costs of Brexit have always been irrelevant,” he will tell his centrist party, which has 12 lawmakers in the 650-seat parliament, according to excerpts of his speech.

“Years of economic pain justified by the erotic spasm of leaving the European Union.”

He will call on the prime minister to stop “kowtowing to her enemies in the Conservative Party” and open “her mind to a ‘People’s Vote’ on the final deal”.

“Deep down, the prime minister knows Brexit is a bad idea. A bad idea whose time has gone,” he will say, adding that rather than feeling sorry for May, people should press her to show “true leadership”.

“She could admit that the Brexit project has gone badly wrong ... by conceding that the deal – any deal, or no deal – that she will bring back from Brussels is not going to be better for Britain than remaining in the European Union.”