Two Tory MPs have been put on ‘defection watch’ by the party amid fears that they are planning to switch to the Liberal Democrats on Boris Johnson’s first day in Downing Street – wiping out his Commons majority at a stroke.

Mr Johnson currently stands to inherit a working majority of four if, as expected, he becomes Prime Minister on July 24 – the day after the new Lib Dem leader succeeds Sir Vince Cable.

Tory whips have been tipped off that if the favourite, Jo Swinson, wins she will announce the defection of two Tory MPs to coincide with Mr Johnson arriving in Downing Street.

Two Tory MPs have been put on ‘defection watch’ by the party amid fears that they are planning to switch to the Liberal Democrats on Boris Johnson’s first day in Downing Street – wiping out his Commons majority at a stroke

Last night Phillip Lee and Guto Bebb, both fervent anti-Brexiteers, denied planning to leave the party.

The Tory whips have called the plan the ‘split screen strategy’, because broadcasters would have to carry live news of the defections at the same time as Mr Johnson entering No 10.

Mr Johnson is also facing the prospect of an immediate no-confidence vote from Jeremy Corbyn if he becomes leader.

Conservative Party chairman Brandon Lewis, members of the backbench 1922 Committee and Chief Whip Julian Smith have all shared fears that Mr Johnson could lose such a vote.

Last night Phillip Lee (left) and Guto Bebb (right), both fervent anti-Brexiteers, denied planning to leave the party

If a new government, either Tory or Labour, cannot subsequently be formed within 14 days, a General Election would be triggered.

If the Conservatives lose the Brecon and Radnorshire by-election this summer, the Tory majority would fall to just three.

Even if Mr Johnson is not hit by defections, arch-Remainers such as former Attorney General Dominic Grieve have indicated that they would vote against Mr Johnson if he tries to take the UK out of the EU without a deal in October.

Even if Mr Johnson is not hit by defections, arch-Remainers such as former Attorney General Dominic Grieve have indicated that they would vote against Mr Johnson if he tries to take the UK out of the EU without a deal in October

In addition, those Cabinet Ministers who expect to lose their jobs under Mr Johnson, including Chancellor Philip Hammond, Justice Secretary David Gauke and Business Secretary Greg Clark, are all expected to resign before he takes over.

Mr Lee said: ‘Others might be happy to trash their political reputations in vain pursuit of personal gain. But a few of us still have the principle and enough courage left to put our country first. It’s hard, though.

‘And I am not sure how much longer the conservatism that I represent can cling on in there.

‘We need people’s active support (ie joining our local Conservative associations) otherwise we won’t be able to carry on fighting for country and party, however much we might want to.’

Cabinet Ministers who expect to lose their jobs under Mr Johnson, including Chancellor Philip Hammond, Justice Secretary David Gauke and Business Secretary Greg Clark, are all expected to resign before he takes over

Mr Bebb said: ‘I have no intention of leaving the party.’

In addition to the anti-No Deal caucus, Mr Johnson faces an equal threat from Tory Brexiteers in the European Research Group, who also say they will bring down the new Prime Minister if he u-turns on his pledge not to delay Brexit beyond October 31, even if it means a No Deal Brexit.

They say they would have ‘no compunction’ about sending letters of no-confidence to the 1922 Committee if he did.

The multiple threats to the stability of Mr Johnson’s embryonic administration are among reasons why both Tory and Labour HQs are planning for an autumn General Election.