Senior Tories fear Rishi Sunak is facing a vicious circle of party ill-discipline, amid concerns that attacks from Boris Johnson, Liz Truss and Suella Braverman will signal his inability to restore authority in the months before the general election.

A rebellion this week over his plans to ban smoking is set to be the latest flashpoint, with libertarian MPs, including Truss, preparing to criticise the proposal as a nanny-state measure that is unconservative.

There is already anger among Sunak’s allies at Johnson, who has made a series of criticisms over the past week, despite hopes that the relationship between the two men had thawed.

One said the former prime minister remained a “bitter, twisted and vengeful” figure after Johnson attacked the foreign secretary, David Cameron, for failing to rule out banning arms sales to Israel and described Sunak’s plan for a gradual smoking ban as “absolutely nuts”.

.During an appearance in the US, Johnson also refused to rule out a political comeback and a return to the Commons, only saying he did not think it was likely in “the short term”.