The Prime Minister said that people should work from home if they can as of Monday.
Boris Johnson confirmed it was time to move to “Plan B” of the Government’s coronavirus strategy, with measures including a return to working from home.
Mandatory mask wearing will be extended to public places like cinemas and theatres from Friday in measures to combat the Omicron variant.
Mr Johnson told a Downing Street press conference: “We will reintroduce the guidance to work from home.
“Employers should use the rest of the week to discuss working arrangements with their employees but from Monday you should work from home if you can.
“Go to work if you must but work from home if you can.
“I know this will be hard for many people but by reducing your contacts in the workplace, you will help slow transmission.”
The NHS Covid pass is to be made mandatory in England in a week’s time for nightclubs and venues where large crowds gather, the Prime Minister also announced.
He said: “It has become increasingly clear that Omicron is growing much faster than the previous Delta variant and is spreading rapidly all around the world.”
While 568 cases had been confirmed in the UK “the true number is certain to be much higher”.
“Most worryingly, there is evidence that the doubling time of Omicron could currently be between two and three days.”
In the Commons, Health Secretary Sajid Javid said Omicron cases could exceed one million by the end of this month on the current trajectory.
“The UK health security agency estimates that the number of infections are approximately 20 times higher than the number of confirmed cases, and so the current number of infections is probably closer to 10,000.
“UKHSA also estimate that at the current observed doubling rate of between two and a half and three days, by the end of this month, infections could exceed 1 million.”
Sajid Javid has warned that the UK faces a “perilous winter” with the Omicron variant infections rising, even with the protection of vaccines.
The Health Secretary told the Commons: “When we set out Plan B, we said that we would act if the NHS was likely to come under unsustainable pressure and with that risk of being able to provide the care and treatment that people need. The Omicron variant has given us cause for concern.”
Speaking of the protection given by vaccines, he added: “Thanks to these defences and our decision to open up in the summer rather than the winter we are much better protected than we were this time last year and we need this protection now more than ever.
“Because although Omicron is becoming more and more prevalent, over the next few days and weeks we will be seeing Delta and Omicron variants circulating together. Facing these twin threats without these pharmaceutical defences would have been hard enough but even with them in place, we still face a perilous winter.”