Officials believe there will be as many as a million cases a day by Christmas, ruining festive plans for households across the country. There are fears hospitalisation will surge in the coming days and risk overwhelming the NHS.

       Mr Johnson is under increasing pressure from scientists to introduce further Covid restrictions to curb the spread of the virus.

       Dr Jenny Harries, chief executive of the UK Health Security Agency, told MPs in Parliament this morning Omicron is "probably the most significant threat we've had since the start of the pandemic".

       She said the "real potential risk" is whether "cases turn into severe disease, hospitalisations and deaths", but added that it is "too early" to be clear on that.

       Meanwhile, Sage member Professor Graham Medley told BBC Radio 4's Today programme: "If the numbers of infections increasing continues in the way that it has done, and it spills out into older age groups, then we could see numbers of people being admitted to hospital getting very large and certainly going over the 1,000, maybe up to 2,000 a day, that we've managed to keep the Delta variant below.

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       "It was sort of below 1,000 since July without any restrictions, but I think that is going to be very, very difficult or are very unlikely to happen."

       The Prime Minister will address the nation at 5pm tonight.

       Despite facing pressure to introduce new restrictions, it is not expected he will impose further regulations but instead urge the public to get booster jabs.

       Preliminary evidence indicates the transmissibility of Omicron means there is little protection from the variant after two doses of a jab.

       However, a booster provides more than 70 percent protection.

       The Government has set itself the ambitious target of giving a third injection to all eligible adults by the end of the month in a bid to stop Omicron requiring more extreme action.

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       So far more than 24 million Britons have had a booster jab.

       More than a million jabs a day must be administered in order to meet the goal of giving an injection to all adults by the end of 2021.

       Yesterday saw just half the figure, with 513,722 booster vaccinations being given.

       Last night MPs in the Commons also voted through a series of measures that aim to help reduce the risk of Omicron.

       They agreed to retrospectively re-introduce mandatory face coverings in indoor spaces and to ask all close contacts of a positive Covid case to take daily tests.

       Despite more than 100 Tory MPs rebelling, they also voted for the implementation of vaccine passports, with large events in England required to see proof of a jab or a negative test from attendees.

       This afternoon the Prime Minister defended the extra measures while saying he understood why Conservatives had voted against them.

       He said: "I respect and understand the legitimate anxieties colleagues have about restrictions on the liberty of the people but I believe the approach that we are taking is balanced and proportionate and right for this country."