UK prime minister Boris Johnson on Wednesday confirmed that England is moving to Plan B measures amid a surge in COVID-19 infections and rising cases of the Omicron variant.

Plan B is a set of measures that would be brought in "if the data suggests the National Health Service (NHS) is likely to come under unsustainable pressure" due to the pandemic.

From Monday, people will be advised to work from home if they can and, from Friday, face masks will become mandatory in most indoor venues.

These venues include theatres and cinemas, although they will not be required when it is not realistic, for example, when people are eating, drinking, exercising or singing. 

Additionally, the NHS COVID-19 pass will also be required for entry into nightclubs and venues where large groups of people gather. These places are 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. 

The passes will still be operational for people who have received two doses of a COVID-19 vaccine. However, this measure will be kept under review. This latest measure will be introduced in a week's time. 

Moreover, the rules for COVID-19 contacts will change whereby, instead of having to isolate, people will be required to take daily tests. This presumably is intended to reduce the impact of another "pingdemic".

Johnson, who spoke during a coronavirus news briefing at Downing Street, said it was clear that Omicron is spreading faster than Delta and that the 568 cases of the variant in the UK is almost certain and underestimate.

"It's now the proportionate and the responsible thing to move to Plan B," Johnson said.

Johnson said further measures could be considered but ruled out the possibility of introducing mandatory vaccinations.

"I didn't want us to have a society in a culture where we forced people to get vaccinated."

On Wednesday the UK reported 51,342 new coronavirus cases, the fourth time in the past week that cases have topped 50,000 in what experts say is a worrying sign.

(With input from agencies)