Professor Alastair Grant, from the University of East Anglia, has predicted the reproduction rate of the new variant based on figures from the UK Health Security Agency (UKHSA).

He said the high figure for Omicron is due to “a mixture of it being good at transmitting itself and being a partial vaccine escape”, adding that it is likely to become the next dominant strain.

Government ministers have warned the Omicron variant would likely be capable of causing a new wave of coronavirus infections that could be even bigger than previous waves.

Ministers are reportedly discussing the potential of stricter Covid measures over Christmas as Omicron cases rise across the UK.

More venues closing and vaccine passports are reportedly being muted while ‘Plan B’ remains the governments back-up plan should the NHS once again get overwhelmed by the new variant.

What’s Plan B?

Vaccine passports would be needed for nightclubs and sport under Covid Plan B. (PA)

The Government’s autumn and winter plan suggested that some measures including the mandatory use of vaccine passports and face coverings could be required in England if cases were putting unsustainable pressure on the NHS.

Should Plan B materialise in the coming months, what would it look like?

Key restrictions to be reintroduced would be face masks, working from home and Covid vaccine passports.

The Plan B proposals draw on the findings of a review into vaccine passports earlier this year, which concluded that certification could help keep events going and businesses open.

Government plans set out how all visitors aged 18 and over to certain events could be required to be fully vaccinated.

The events listed are all nightclubs, and other venues open after 1am with alcohol, music, and dancing, and indoor events with 500 or more attendees where they are likely to stand and mix to a significant degree, or move around during the event, such as music venues or large receptions.

The plan also includes outdoor, crowded settings with 4,000 or more attendees where they are likely to stand, or move around during the event, such as festivals, and any settings with 10,000 or more people, such as large sports and music stadia.

Detailing when restrictions could be introduced in September, a government document stated: “The Government recognises this causes more disruption and has greater immediate costs to the economy and some businesses than the other Plan B interventions, so a final decision would be made based on the data at the time.”

It adds: “If Plan B is implemented, the Government will bring back the legal requirement to wear face coverings in some settings.

“The precise settings will be decided at the time.”

The PM’s official spokesman said: “There is absolutely no plan to introduce Plan B currently. (PA)

The PM’s official spokesman said: “There is absolutely no plan to introduce Plan B currently. We retain that capability if required if we believe the NHS is coming under unsustainable pressure.

“We obviously keep very close watch on the latest statistics. We always knew the coming months would be challenging.”