Boris Johnson has said that he is not immediately imposing any further Covid restrictions, but will not hesitate to do so if the data shows it is necessary.

       Speaking at the end of a two-hour emergency meeting of cabinet, Mr Johnson said that the arguments for and against going beyond the current Plan B restrictions were “finely balanced”.

       He said that ministers had agreed that the data on infections, hospitalisations and deaths should be kept under “constant review” on an hour-by-hour basis.

       And he said he would not hesitate to take further action to protect public health if the data showed it to be needed.

       The prime minister’s scientific advisers have warned that action is needed urgently to save the NHS from being overwhelmed.

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       Minutes of advisory group Sage’s last meeting on Thursday warned “more stringent measures would need to be implemented very soon” to prevent hospitalisations reaching thousands per day.

       And the Sage experts warned that delaying until the New Year would “greatly reduce the effectiveness of such interventions and make it less likely that these would prevent considerable pressure on health and care settings”.

       Scientists have reportedly offered Mr Johnson three options for potential action - non-legally binding advice to families to limit indoor mixing over the Christmas period; new restrictions on indoor mixing, a return of social distancing and an 8pm curfew on pubs and restaurants; or a full-scale “firebreak” lockdown.

       Mr Johnson said: “I agree that the situation is extremely difficult and the arguments either way are very, very finely balanced.

       “We’ve got cases of Omicron surging across the country now we’ve got hospitalisations, rising quite steeply in in London and the obvious conclusion is that of course it was right to go fast to Plan B in the way that we did and also right to double the speed of the booster rollout.”

       But he said that there were “risks and uncertainties” surrounding the rate at which people infected with Omicron are likely to end up in hospital, the severity of any illness caused and the effectiveness of the booster vaccine in fighting off the variant.

       “We agreed that we should keep the data from now on under constant review, keep following it hour by hour,” he said.

       “Unfortunately, I must say to people we will have to reserve the possibility of taking further action to protect the public and to protect public health and to protect our NHS, and we won’t hesitate to take that action.”

       Mr Johnson added: “In the meantime what I would say to everybody is ‘Please exercise caution as you go about your lives. Please think of the guidance and protecting yourself and your loved ones.

       “‘And please get a booster. Please get a vaccination.’

       “It could not be more urgent. There are still millions of people in this country who haven’t got a vaccination and it makes such a difference. The evidence is overwhelming. It’s such a positive thing to do.

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       “And I say to all those people who are vaccinated whether out of apathy or whatever reason, please, please please think of this as a great thing to do for yourself and for your family to get boosted now.”