Boris Johnson has announced new Covid restrictions in England amid concerns about the spread of the Omicron variant.
Speaking at a Downing Street press conference on Wednesday evening, the prime minister said people should once again work from home where possible from Monday.
Johnson said vaccine passports will be required for some venues where large crowds gather, including nightclubs, from next Wednesday.
Proof of double vaccination or a negative lateral flow test will be needed for unseated indoor venues with more than 500 people, unseated outdoor venues with more than 4,000 people and any venue with more than 10,000 people.
Mandatory mask wearing will be expanded from Friday to “most public indoor venues”.
The tightening of the rules comes amid widespread anger about accusations that No.10 staff held a Christmas party last year that broke lockdown rules.
Johnson said: “We can’t yet assume that Omicron is less severe than previous variants.
“While the picture may get better, and I sincerely hope that it will, we know that the remorseless logic of exponential growth could lead to a big rise in hospitalisations and therefore, sadly, in deaths.
“That’s why it is now the proportionate and the responsible thing to move to Plan B in England.”
The new rules will be reviewed in early January at the latest, Johnson said.
Speaking at the same time in the Commons, Sajid Javid warned that the UK faces a “perilous winter” with Omicron infections rising, even with the protection of vaccines.
The health secretary said there are 568 cases of Omicron confirmed but that the true figure is estimated to be “probably closer to 10,000”.
This article originally appeared on HuffPost UK and has been updated.