Support for British Prime Minister Boris Johnson and his ruling Conservative Party has plummeted after a series of scandals, with a majority of voters thinking he should now resign, according to a poll published on Saturday.

Johnson has found himself facing criticism on a number of fronts in recent weeks from the funding of the refurbishment of his Downing Street flat to a claim he intervened to ensure pets were evacuated from Kabul during the chaotic Western withdrawal in August.

The most damaging has been...