Boris Johnson said the latest record Covid case figures showed that those who believed the pandemic to be over were 'profoundly wrong.'
Speaking at a press briefing in Downing Street, the Prime Minister said: 'Our United Kingdom is in the midst of the fastest growth in Covid cases that we’ve ever known.
'Previous waves of the pandemic didn’t have a single day with more than 100,000 new cases reported, one day last week we had 200,000 people test positive.
'And the latest figure today is another 218,000, though that includes some delayed reports.
'So anyone who thinks our battle with Covid is over, I’m afraid is profoundly wrong.
'This is a moment for the utmost caution.'
The Prime Minister said, despite the high number of coronavirus cases being recorded in the UK, there was a 'chance' extra restrictions would not be needed in England.
Boris Johnson told a press briefing in Downing Street: “But our position today differs from previous waves in two crucial respects.
'First, we now know that Omicron is milder than previous variants, so while hospital admissions are rising quickly, with over 15,000 Covid patients now in hospital in England alone, this is not yet, thankfully, translating into the same numbers needing intensive care that we saw in previous waves.
'Second, thanks to the fantastic national effort to get Britain boosted, we now have a substantial level of protection, higher than any of our European neighbours, with over 34 million boosters administered, including in England reaching more than 90% of the over 70s and 86% of the over 50s.
'And so, together with the Plan B measures that we introduced before Christmas, we have a chance to ride out this Omicron wave without shutting down our country once again.
'We can keep our schools and our businesses open and we can find a way to live with this virus.'
Chief Medical Officer for England Professor Chris Whitty (left) and Prime Minister Boris Johnson during a media briefing in Downing Street, London, on coronavirus (Covid-19).
Tolga Akmen
He went on: 'The disruptions we face can be far less sever than a national lockdown.'
'The government is acting.. to fortify our NHS to face the challenges ahead.'
He confirmed that from the 10th of January 'critical workers' will be able to take lateral flow tests, with the government pledging to provide 100,000 of them.
'We're increasing NHS capacity by building on-site Nightingale hospitals', he said.
'We've bought more anti-virals per person than anywhere else in Europe.
'As our NHS moves to a war footing I will be recommending to cabinet tomorrow that we continue with plan B.
'The public have responded and changed their behaviour... buying valuable time to get boosters in arms.'
Prime Minister Boris Johnson watches as Esther (surname not given), 19, receives her Covid-19 booster vaccine during a visit to a vaccination hub in the Guttman Centre at Stoke Mandeville Stadium in Aylesbury, Buckinghamshire, as the booster vaccination programme continues.
Steve Parsons
Mr Johnson pleaded: 'Work from home if you can, wear face coverings on pub transport... take a test before you go to a high-risk venue or meet those who are elderly or vulnerable.
'If you haven't already done so, please please get that booster.'
Boris Johnson has said people are dying “needlessly” because they have not been properly vaccinated against Covid-19.
“There are still almost nine million people eligible, who haven’t had their booster,” he told a Downing Street news conference.
“It’s absolutely heart-breaking that as many as 90% of those in intensive care with Covid have not had their booster, and over 60% of those in intensive care, who have Covid, have not had any vaccination at all.
“People are dying needlessly because they haven’t had their jabs, they haven’t had that booster.”