Rishi Sunak has said Boris Johnson was “right to apologise” for attending a Downing Street lockdown party as he offered a lukewarm endorsement for the embattled prime minister.

       The chancellor, who chose to skip Mr Johnson’s grilling over the partygate scandal at PMQs on Wednesday, instead travelling to Devon to discuss a jobs announcement, added in a tweet several hours after the event that he supported the PM’s “request for patience” as Sue Gray conducts her investigation.

       Rather than offer support to the beleaguered prime minister in the House of Commons, Mr Sunak – a favourite to replace Mr Johnson at No 10 according to some pollsters – visited a company purifying pharmaceutical drugs.

       Following speculation over why he had not publicly supported Mr Johnson earlier in the day, the chancellor said on Twitter: “I’ve been on a visit all day today continuing work on our ￡PlanForJobs as well as meeting MPs to discuss the energy situation.”

       MPs including Labour’s Karl Turner noted it was “hardly a ringing endorsement”.

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       The chancellor took until after 8pm to share the message. Conservative MP Jacob Rees-Mogg told the BBC’s Newsnight programme the delay was because the chancellor had had a “busy day”.

       Other senior Tories have expressed more full-throated support for the PM.

       Foreign Secretary Liz Truss, who is also seen as a potential leadership contender, tweeted: “The Prime Minister is delivering for Britain - from Brexit to the booster programme to economic growth.

       “I stand behind the Prime Minister 100% as he takes our country forward.”

       It comes after a bruising day for Boris Johnson. Earlier this week, a leaked email showed around 100 No 10 staff were invited to a drinks gathering in Downing Street’s rose garden while the country was still subject to strict Covid lockdown restrictions.

       At PMQs, Mr Johnson apologised for attending the 20 May 2020 party – but insisted he thought it was a “work event”.

       After days of stonewalling questions, the prime minister told MPs he acknowledged the “rage” of the public “with me and with the government I lead when they think in Downing Street itself the rules are not being properly followed by the people who make the rules”.

       Deputy Prime Minister and Justice Secretary Dominic Raab told ITV it was a “daft question” when asked whether he would run again for the Tory leadership.

       “I’m fully supportive of this Prime Minister and I’m sure he will continue for many years to come,” he said.

       Home Secretary Priti Patel and Business Secretary Kwasi Kwarteng are reported to have expressed their support in a Whatsapp group for Tory MPs.

       Health Secretary Sajid Javid said: “I completely understand why people feel let down. The PM did the right thing by apologising.

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       “Now we need to let the investigation complete its work. We have so much to get on with including rolling out boosters, testing and antivirals - so we can live with Covid.”

       Transport Secretary Grant Shapps told Times Radio: “I think the prime minister was very contrite today, he apologised and he took full responsibility.”