Liberal Democrat leader Sir Vince Cable is set to accuse Theresa May of putting ‘the interests of the country second to the whims of the extremists in her party’.
Brexit will be at the heart of his keynote Lib Dem conference speech in Brighton.
Sir Vince will also demand May shows ‘true leadership’ by accepting the growing calls for a people’s Vote on the final Brexit deal.
He is expected to say: ‘I would go so far as to say that some of us are starting to feel sorry for the prime minister. It seems that even the European leaders are moved to pity. It is obvious why.
‘She is dutifully delivering a policy she doesn’t really believe in; failing in negotiations; losing public support; and all to appease a dwindling group of angry people in her party who will denounce her as a traitor, whatever she comes up with.
‘But when we feel sorry for the country’s prime minister, something is seriously wrong.
‘Our sympathy can only extend so far, while she puts the interests of the country second to the whims of the extremists in her party.
‘Deep down, the Prime Minister knows Brexit is a bad idea. A bad idea whose time has gone.
‘Even now, Theresa May could shock us all, by displaying 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.
‘Instead of kowtowing to her enemies in the Conservative Party, she could lead her party and the country by opening her mind to a ‘People’s Vote’ on the final deal.’
Sir Vince will also attack ultra Brexiteers who he claims do not care about the damage leaving the EU will wreak on the UK.
‘For the ‘True Believers’ – the fundamentalists – the costs of Brexit have always been irrelevant,’ he is expected to say. ‘Years of economic pain justified by the erotic spasm of leaving the European Union.
‘Economic pain felt – of course – not by them by those least able to afford it. And the latest piece of nastiness from Jacob Rees-Mogg – calling into question the right of Europeans to stay in Britain and of Britons to stay in Europe: creating unnecessary worry and insecurity for millions.
‘The public don’t mind what these people dream about behind closed doors – so long as their dreams don’t become nightmares for the rest of us. It really beggars belief that the army and the police are now being asked to prepare for riots in the chaotic aftermath of a botched Brexit.
‘And billions – billions – of taxpayers’ money spent preparing for disaster.’