Liz Truss insisted she was running a “positive” bid to become prime minister as allies distanced her campaign from Nadine Dorries’ decision to retweet a mocked-up image of Rishi Sunak stabbing Boris Johnson in the back.

The Foreign Secretary said she had been “very clear” with her team about the type of campaign she wanted to run.

Culture Secretary Ms Dorries, a high-profile supporter of Ms Truss, shared a doctored image on Twitter that portrayed Mr Johnson as Julius Caesar with Mr Sunak as one of the assassins.

A string of Conservative MPs – mostly supporters of Mr Sunak – quickly condemned Ms Dorries and branded the attacks on the former chancellor as “dangerous” in the wake of the murder of Sir David Amess.

Asked about Ms Dorries’ actions, Ms Truss said: “I’ve taken Twitter off my phone for the duration of this campaign.

“I’ve been very clear with all of my team, I’m running a positive campaign. This is about growing the economy, it’s about unleashing the potential right across the UK.”

Work and Pensions Secretary Therese Coffey, Ms Truss’ campaign manager, told Times Radio it was Ms Dorries’ personal choice to post the message.

Ms Coffey said: “Well, I wouldn’t have done it. The Liz for Leader campaign certainly didn’t do it. Nadine chose to do it. I’ve made her aware that many colleagues were upset by it.

“It’s for Nadine to decide how she runs her social media. But all I say is that I’m really here to focus on Liz rather than other news.”

She added: “I’m not going to go into individual conversations, but she recognised that other people would have been upset by some of this, but she’s very keen to make the case herself.”

The former chancellor was asked about accusations he is a “backstabber” on the BBC Radio 4 Today programme, but said he would not comment specifically on “what others are choosing to say”.

He added: “I will tackle the broader claim that they (the accusations) relate to, because I do think there is a risk that people are looking at the last few months of the Government with slightly rose-tinted glasses about what it was really like.

“Because it wasn’t working as it should, and crucially the Government found itself on the wrong side of a very serious ethical issue, and, for me, also going down the wrong economic path, and that’s why in the end more than 60 MPs at the last count, I think, resigned from the Government, of which I, after a lot of deliberation and months of standing by the PM, was one of them.”