Boris Johnson could face a second leadership challenge within six months – even if he were to survive one in the coming weeks – under “live” proposals being discussed by backbench Tories.

With Sue Gray’s report into Downing Street parties now expected as soon as Wednesday, there is renewed speculation that her findings will trigger a wave of letters of no confidence in the Prime Minister.

Should the threshold of 54 letters be hit, allies of Mr Johnson have said they are confident that he could survive the subsequent confidence vote.

A total of 181 MPs – more than half the parliamentary party – would need to vote against the Prime Minister for him to be removed from office.

However, senior Conservative sources have revealed that even if he were to survive, he is unlikely to be immune from another challenge for 12 months, as is currently the case.

Instead, two insiders said there was “live discussion” among the executive members of the 1922 Committee of backbench Tory MPs over whether the grace period should be halved to six months.