Brexit: Tory election guru and Boris Johnson ally Lynton Crosby plots to torpedo Theresa May's plans

Sir Lynton headed two successful London Mayor campaigns for the ex-foreign secretary

Theresa May’s premiership has suffered a severe blow after reports emerged that Tory election-guru Sir Lynton Crosby is running a campaign to kill off her Brexit proposals.

Sir Lynton is said to have ordered allies to work with hardline Brexiteers in the European Research Group (ERG) of Tory MPs to bring Ms May’s ‘Chequers’ deal down, something that could well lead to her fall.

Many ERG members back Boris Johnson as a future leader, and with Sir Lynton also having run two successful mayoral campaigns for him, the strategist’s appearance now is seen as a sign of growing momentum behind the ex-foreign secretary’s ambitions.

It came as Ms May attempted to stiffen her support among Brexiteers – who think her plans will keep the UK too closely aligned with Brussels, by saying she will not be pushed around by the EU in negotiations and repeating her vow to deliver on the 2016 referendum.

Sir Lynton, who also advised Tory leaders in the 2015 election victory and last year’s shock poll when the Tories lost their majority, has sent a senior member of his firm CTF Partners to work with the ERG, The Sunday Times reported.

David Canxini will partner up with ex-Brexit minister Steve Baker, a key organiser in the Conservative Leave campaign ahead of the 2016 referendum.

The newspaper reports that one option is to revive the campaign group Change Britain, with some seeing it as possible future platform for a Mr Johnson leadership drive.

But senior Tory sources were said to have warned that Mr Johnson’s leadership ambitions were destabilising Brexit and could lead to it falling through altogether.

The Sunday Times also reported that PM’s aides have held talks with senior civil servants about whether to call a general election if a Brexit deal is rejected by MPs.

With Brussels demanding further compromise, and a significant number on her own benches set to vote the deal down, let alone Labour, the odds are stacking up against Ms May’s deal passing through parliament.

But the Prime Minister remained defiant and stood by her plan, writing in the Sunday Telegraph: “I will not be pushed into accepting compromises on the Chequers proposals that are not in our national interest.”

The PM also dismissed calls for a “People’s Vote” on the terms of withdrawal.

She said: “To ask the question all over again would be a gross betrayal of our democracy.”

The Independent has been running its own campaign for a Final Say referendum on whatever the outcome of Brexit is with almost three quarters of a million people having signed the petition.

Ms May also said Britain would get through a no-deal outcome and “thrive”.

But in the same newspaper high-profile Tory MP Nick Boles, who backed Remain at the referendum, came out against the Chequers deal.

He wrote that under current the plans, the UK faces “the humiliation of a deal dictated by Brussels”, which is treating the Chequers proposals as an “opening bid”.