Boris Johnson has pulled out of a planned visit to Lancashire “due to a family member testing positive for coronavirus”, Downing Street has said.
It comes as the prime minister faces calls from some of his own MPs to resign after he admitted he attended the No.10 garden party in May 2020.
Johnson apologised on Wednesday for attending a “bring your own booze” gathering when the rest of the country was in lockdown.
The PM insisted he thought the party was work-related, but said he recognised “with hindsight I should have sent everyone back inside”.
He said an inquiry headed by senior official Sue Gray was examining the situation but accepted “there were things we simply did not get right and I must take responsibility”.
The scandal prompted furious Tory MPs to call for the prime minister to resign.
And although Cabinet ministers jumped into action to defend Johnson, the late interventions of Foreign Secretary Liz Truss and Chancellor Rishi Sunak – both tipped as potential successors – did little to instil confidence in his future.
Sunak had notably spent the day away from London on a visit in Devon.
Johnson faced open revolt from one wing of his party, as MP for Moray and Scottish Conservative leader Douglas Ross called on him to quit.
He was joined by all 31 Tory MSPs, according to reports.
In Westminster, three other MPs joined their cause – Sir Roger Gale (North Thanet), Caroline Nokes (Romsey and North Southampton), and chairman of the Public Affairs and Constitutional Affairs Committee William Wragg (Hazel Grove).
Leader of the House Jacob Rees-Mogg dismissed those who were calling for Johnson to go as “people who are always unhappy”.
But a poll for The Times by YouGov, which was carried out before Johnson’s apology at Prime Minister’s Questions, put Labour at a 10-point lead ahead of the Tories for the first time in nearly a decade.