Bookmakers have shortened the odds on Boris Johnson being replaced as prime minister following outrage over the “Partygate” scandal regarding a string of lockdown-breaking social events that occurred behind the scenes in Westminster in May, June, November and December 2020 and April 2021.

       The PM, his chancellor Rishi Sunak and his wife Carrie Johnson were among the latest tranche of government staff members handed fixed penalty notice fines by the Metropolitan Police for breaking their own rules to stage parties during the Covid-19 pandemic.

       Both Mr Johnson and Mr Sunak have apologised and paid their fines, with Mr Johnson saying: “In all frankness at that time it did not occur to me that this might have been a breach of the rules. Of course, the police have found otherwise and I fully respect the outcome of their investigation.”

       But he brushed off calls for his resignation, saying: “I believe it’s my job to get on and deliver for the people of this country. That’s what I’m going to do.”

       However, as the first serving PM to be found to have broken the law, he has already come under intense pressure to resign from Labour leader Sir Keir Starmer and from campaign groups like Covid-19 Bereaved Families for Justice.Leading backbench critics of Mr Johnson such as Sir Roger Gale and Scottish Conservative leader Douglas Ross have, however, argued that it is “not the time” for Britain change leaders in light of the war raging in Ukraine.

       Recommended Boris Johnson news - live: First MP calls for PM to quit as Shapps says ‘humans make mistakes’ Boris Johnson broke law ‘in error’ and is ‘completely mortified’ by fine, minister claims Will Boris Johnson resign?

       The No 10 drinks parties held in the midst of England’s coronavirus lockdowns remain the subject of the Met’s ongoing investigation and Whitehall mandarin Sue Gray has still yet to deliver her full report into what went on behind closed doors.

       Ms Gray did submit her long-delayed report into Partygate to the PM in January and a 12-page “update”, heavily-redacted at the request of the Met, was released, in which the civil servant blasted “failures of leadership and judgement” in Downing Street and the Cabinet Office, describing the behaviour of some personnel as “difficult to justify”.

       In a scathing comment on the culture at No 10 under Mr Johnson’s leadership, the senior civil servant wrote: “Some of the gatherings in question represent a serious failure to observe not just the high standards expected of those working at the heart of government but also of the standards expected of the entire British population at the time”.

       Since the publication of her partial report in January, the outbreak of Russia’s war in Ukraine has enabled Mr Johnson to rehabilitate his public image by leading the international response to Vladimir Putin’s actions, imposing harsh economic sanctions, sending weapons and aid and even visiting Kyiv to tour the city in the company of president Volodymyr Zelensky, an important show of solidarity.

       Meanwhile, his most likely challenger for the Tory leadership, Mr Sunak, has endured a torrid time of it, under fire over the cost of living crisis, his own tax affairs and now his own fine over Partygate.

       But only a leader as brazen and shameless as Boris Johnson could hope to survive the present outrage, especially given that a new YouGov poll has concluded that 57 per cent of the British public believes that he and the chancellor should resign.

       According to Smarkets, there is now a 30 per cent chance that Mr Johnson will leave Downing Street in 2022 but could climb further if Cabinet colleagues call for his resignation or if Mr Sunak sets a precedent by resigning himself, a possibility they think is better than even at 55 per cent.

       The betting company says there is a 14 per cent of the PM stepping down by June but a 54 per cent likelihood of his facing a vote of no-confidence at the instigation of his own Conservative backbenchers.

       Should Mr Johnson go, the race for his successor is wide open, with Liz Truss (15 per cent), Tom Tugendhat (11 per cent) and Jeremy Hunt (10 per cent) the leading contenders.

       Recommended Ukraine news live: Putin hails invasion as ‘noble’ Why has Russia invaded Ukraine? The conflict simply explained Sign The Independent’s petition to help the people of Ukraine

       The scandal-hit Mr Sunak is down in sixth place, having been hot favourite earlier this year.

       Patrick Flynn, political analyst at Smarkets, commented: “The news that Boris Johnson and Rishi Sunak have been fined by the police, alongside controversy surrounding the chancellor’s tax affairs, has massively changed the dynamics of the prime minister’s potential exit and his eventual successor. That Sunak’s prospects have taken a battering over the last month means Johnson is though safer than he otherwise would have been.”