Although it is understood that Ms Truss does not consider her position on Covid regulations to be a bid for the Tory leadership, sources close to the Foreign Secretary have said she is sceptical about existing Plan B rules and concerned about proposals to introduce more regulations as omicron cases rise.

“It smells like she’s trying to heavily position herself as a Conservative libertarian… it reeks of desperation and it’s all a bit pathetic,” a source told The Times.

‘It will backfire for her over the coming months’

On Wednesday, a senior Tory insider told The Telegraph: “It will backfire for her over the coming months. If you are going to make interventions that can be read as leadership ambition, they have to be well timed.

“She is just constant and so naked about it. It winds people up. I think she has gone too early on all this.”

One government source said Ms Truss would garner more support with Tory members if she was more supportive of Mr Johnson and used her new portfolio as Brexit minister to resolve ongoing problems with the Northern Ireland protocol.

“Anyone’s best way of becoming the next leader is to help the PM do as good a job as possible for the rest of the Parliament,” the source said. “I think sorting out the protocol is a far better route to leadership than this.”

Ms Truss consistently rates highest in a poll of Conservative members conducted regularly by the Conservative Home website. In the latest version, she had a net approval rating of 82 per cent with members.

Lord Frost, who recently resigned from the Cabinet over the Government’s positions on Covid and taxation, polled second with 73 per cent.