The survey will come as a blow to Mr Johnson as he faces growing questions over his own involvement in the gathering — after a leaked email showed over 100 Downing Street staff were invited to “bring your own booze” event on 20 May, 2020.
At the time, England was still emerging from the first strict national lockdown to contain the spread of Covid, with members of the public banned from meeting more than one other person outdoors.
According to the pollsters Savanta ComRes, a clear majority (66 per cent) said the prime minister should now resign, including 42 per cent of those who cast their vote for the Conservatives at the 2019 winter election.
It represents a 12-point increase on a previous snap poll by the organisation in December in the wake of separate allegations of a party held at No 10 during the winter of 2020 when London faced tough Covid restrictions.
Of the 1,040 UK adults surveyed, Savanta ComRes added that under a quarter (24 per cent) said the prime minister should not resign.
When asked whether Mr Johnson was still an “asset” to the Tory party, those who voted for the party in 2019 were equally divided, with 45 per cent saying he was no longer an asset and 45 per cent suggesting he remained and asset.
A further 65 per cent of those polled said Martin Reynolds, a senior civil servant and the prime minister’s principal private secretary who sent the email to No 10 staff ahead of the 20 May event, should also resign.
Chris Hopkins, the political research director at Savanta ComRes, said: “A 12pt increase in those saying he should resign compared to Christmas party-gate is is significant, but ultimately it’s not the court of public opinion that Johnson will be tried in; it’s his own party”.
He added: “If, as in December, the scandal leads to the Conservative vote share collapsing in the opinion polls, the doubts among among those who used to see Johnson’s electoral successes as his saving grace will no doubt increase, and the major difference between now and early December is that the Tories do not have a poll lead to act as a cushion to break the PM’s fall.
“Increased Labour leads that point to Keir Starmer in No.10 really could see Tory backbenchers get tetchy, and they may start the wheels in motion to replace Johnson as prime minister.”
The poll coincided with a separate survey from YouGov, which also found 56 per cent of people thought the prime minister should resign, with 27 per cent saying he should remain in post and 17 per cent saying they did not know.
When a similar question about whether Mr Johnson should remain as leader of the Conservative Party was posed by YouGov on November 22, 48 per cent said he should stand down, piling pressure on the prime minister.
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