Professor Chris Whitty has warned a “significant increase in hospitalisations” is coming from Omicron, with Boris Johnson telling ministers to expect a “huge spike” in infections.

The stark messages delivered to the Cabinet came as almost 60,000 new Covid-19 cases were reported, the highest total since January 9, driven by the surge in the highly-transmissible variant.

Health Secretary Sajid Javid told MPs there was a “very real risk” that the exponential rise of Omicron cases could translate into a rise in hospital admissions that “threatens to overwhelm the NHS”.

England’s chief medical officer Prof Whitty told a virtual Cabinet meeting on Tuesday that it is “too early to say how severe” the strain is after early suggestions from South Africa that it could be relatively mild.

Mr Javid told MPs that even if Omicron did turn out to be less severe than the Delta variant, the fact it was so easily spread meant “it still has the potential to overwhelm the NHS”.

Downing Street did not reject a suggestion that new Omicron cases could hit a million per day next week based on a “valid” estimate from the UK Health Security Agency that daily infections are currently around 200,000.

Ministers hope the Plan B measures on masks and Covid passes announced for England will slow the spread of Omicron long enough to substantially increase the number of people who have received booster jabs.

The latest daily figures showed 513,722 booster or third doses were reported on December 13 – below the rate of around a million jabs a day required to meet the Government’s target of offering another shot to all eligible adults by the end of the year.

MPs were voting on the Plan B regulations in the Commons on Tuesday, with the measures expected to pass despite the expectation there will be a revolt on the Tory benches.

Deputy Prime Minister Dominic Raab insisted the restrictions, including mandatory mask-wearing and the use of Covid health certificates for large venues, will be sufficient over Christmas, meaning families can “spend it with loved ones”.

But Scottish First Minister Nicola Sturgeon urged people across Scotland to limit their mixing by socialising with only up to two other households indoors either side of Christmas.

And the downbeat assessment from Prof Whitty delivered to the first Cabinet meeting not to take place in person for months will raise concerns that additional measures may be needed in England in the new year.

Earlier, South African Medical Association chairwoman Dr Angelique Coetzee told MPs on the Science and Technology Committee that most cases of Omicron have been mild.

In other developments:

– UK Health Security Agency chief medical adviser Susan Hopkins said the country will need “some level of restrictions in place” for the next four to eight weeks.

– People were left temporarily unable to book PCR test slots at walk-in or driver-through sites in England due to “exceptionally high demand” while demand for home-delivered lateral flow tests again exceeded the ability to send them out.

– Hotel quarantine for travellers arriving in England will be abandoned from 4am on Wednesday with all 11 countries on the red list removed because the spread of Omicron in the UK meant the measure to prevent cases being imported was less effective.

– NHS Providers chief executive Chris Hopson said the health service was already “beyond full stretch” even before the expected increase in Omicron hospital admissions.

– As of 9am on Tuesday there had been a further 59,610 lab-confirmed Covid-19 cases in the UK and 150 more people had died within 28 days of testing positive.

– The 15-minute observation period after a Pfizer or Moderna jab will be suspended after the UK’s four chief medical officers said it “will cause more harm than it can avert” because of the impact on the number of vaccines that can be administered.

In the Commons, as MPs debated the new restrictions for England, Mr Javid said: “Unfortunately there is now a very real risk that the exponential rise of Omicron cases translates into a spike of hospitalisations that threatens to overwhelm the NHS.”

He said the scientists “have never seen a Covid-19 variant that’s capable of spreading so rapidly”.

But Tory critic Andrew Bridgen said: “In my view the most dangerous epidemic sweeping the world and sweeping our country is an epidemic of fear. “