Boris Johnson could attempt to make a political comeback like “Berlusconi or Trump”, according to a former Tory minister.

Rory Stewart, an ex-Conservative MP who ran for the leadership in 2019, accused the outgoing prime minister of having “an extraordinary ego” and believing he was “badly treated” when ousted from Downing Street.

He told the BBC that Mr Johnson “doesn’t see the reality, which is he was a terrible prime minister and that he lost his job because of deep flaws of character”.

Pointing to the former Italian prime minister who at 85 has spoken of his desire to return to politics, as well as the ongoing debate in the American Republican party, Mr Stewart added: “I fear we are going to end up with a second [Silvio] Berlusconi or a second [Donald] Trump trying to rock back in again.”

The former international development secretary’s remarks come with a week to go until we find out the winner of the Tory leadership contest between Liz Truss and Rishi Sunak, with the victor also taking the keys to Downing Street.

Polling has suggested Conservative voters would choose Mr Johnson to stay on over either candidate if they had the chance.

And some MPs have been talking about “buyers’ remorse” over the party driving him out of office because of his appointment of Chris Pincher as chief whip, despite allegations of inappropriate behaviour, as well as the partygate scandal and other ethical issues.

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In a separate interview with the Guardian, Mr Stewart called the PM “dangerous”, but said there were still “people who want him back” within the party.

He added: “I think we need to remind people why he left. He should have gone much, much earlier. What he did was deeply, deeply shameful – and dangerous.”

Asked by the BBC about whether politics would improve now Mr Johnson is leaving office to be replaced by Ms Truss or Mr Sunak, the ex-MP said “the jury’s out”.

Appearing to take issue with Ms Truss’ campaign, which has focused on cutting taxes, he said: “One of the things that is worrying is the tendency of everybody, and I think all candidates get dragged into this, to make promises that sound fine but either can’t be delivered or turn out to be damaging.

“I am particularly worried about these promises of tax cuts particularly at a time when inflation is taking off and when I think our public sector needs support.”

But it seems unlikely Mr Stewart is planning a return to frontline politics himself, having just been confirmed as the new president of GiveDirectly – an international charity which helps donors send money straight to the world’s poorest households.