Boris Johnson is drawing up a list of officials to offer resignations over Partygate in a bid to salvage his premiership, The Independent has learned.

       Dubbed “Operation Save Big Dog” by the prime minister himself, the blueprint includes a drive to work out which heads should roll following the publication of senior official Sue Gray’s findings, as well as highlighting the prime minister’s achievements, according to sources. Officials have also started using the code name, The Independent understands.

       Dan Rosenfield, Boris Johnson’s chief of staff, and Martin Reynolds, his private secretary and author of the “BYOB” email, are thought to be possible candidates for departure.

       While putting names to the plan is a matter of hot debate, a more broadly accepted idea is that at least one senior political appointee and a senior official must be seen to leave Downing Street over the affair, as both groups share blame, two Whitehall sources said.

       A former Tory cabinet minister told The Independent that, although they backed Mr Johnson, they believed a “root and branch” overhaul of No 10 and parts of the Cabinet Office would prove essential to move on from Partygate. It would be a “bare minimum to translate contrition into action”, they said.

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       The “save big dog” plan includes a communications “grid” in the lead up to the investigation’s conclusion and beyond. This comprises lines for supportive ministers to take in press interviews, emphasising a contrite prime minister and listing his achievements amid the difficult choices posed by the pandemic.

       The operation also includes sounding out support among backbenchers for possible leadership rivals including chancellor Rishi Sunak, foreign secretary Liz Truss and even former health secretary Jeremy Hunt.

       Mr Hunt is unlikely to command enough support to win the leadership, but No 10 aides believe could play an important role in any leadership contest.

       The plan reflects how precarious the position of Downing Street and the Cabinet Office has become following a slew of highly detailed reports on parties amid Covid-19 restrictions.

       On Friday, the former director general of the government’s Covid taskforce posted an apology on social media for holding leaving drinks in the Cabinet Office during coronavirus restrictions days before Christmas in 2020.

       Kate Josephs, chief executive of Sheffield City Council, said she was cooperating with a probe by senior civil servant Sue Gray and admitted to a “gathering … with drinks, in our office”.

       It followed an apology from Downing Street to Buckingham Palace after reports from The Daily Telegraph of two No 10 parties held on the eve of Prince Philip’s socially distanced funeral.

       Officials have refused to confirm or deny if Boris Johnson was aware of these parties, after he admitted to attending at least one drinks party and was pictured at a second. On Friday the prime minister’s spokesman said: “It is deeply regrettable that this took place at a time of national mourning and No 10 has apologised to the palace.”

       It is not clear if Downing Street admitted, in its apology to the palace, to having breached Covid rules with a social gathering. One of the gatherings was a leaving party for Mr Johnson’s director of communications, James Slack, who said on Friday that the “event should not have happened at the time that it did”.

       Downing Street also refused to comment on the existence of a plan to save Mr Johnson, but when asked about the name “Operation Save Big Dog”, a spokesperson said: “We absolutely do not recognise this phrase.”

       Polling for The Independent revealed voters are deserting Mr Johnson over the party scandal, with 70 per cent calling for him to quit and almost as many dismissing his Commons apology as bogus.

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       The survey, by Savanta, found that just 21 per cent backed the prime minister to stay in power.

       Just as worryingly for the embattled leader, 68 per cent did not consider his apology – in which he claimed he did not realise a “bring your own booze” gathering in his garden was a party – to be genuine.