England’s chief medical officer has warned people not to mix with others unless they have to in the run-up to Christmas after Britain confirmed its most daily coronavirus cases since the start of the pandemic.

With a new highly transmissible Omicron variant of the virus surging across Britain, a further 78,610 COVID-19 infections were reported on Wednesday (local time), about 10,000 more than the previous high reported last January.

Chief medical officer Chris Whitty said Britain was being hit by “two epidemics on top of each other” as he urged the public to scale back their Christmas plans.

“People should be prioritising those things – and only those things – that really matter to them,” he told a news conference.

“Don’t mix with people you don’t have to.”

Professor Whitty warned that the number of daily cases would continue to break records in the next few weeks and a big rise in hospitalisations was “a nailed-on prospect”.

Prime Minister Boris Johnson agreed with a “general instinct to be more cautious” but ruled out further government restrictions for now.

“We’re not cancelling events, we’re not closing hospitality, we’re not cancelling people’s parties or their ability to mix,” he said.

More than 11 million people have tested positive for the disease since the start of the pandemic in Britain, which has a total population of about 67 million.

While the number of daily cases is at a record, deaths are running at a much lower level than earlier in the pandemic.

The government hopes that a rapid booster rollout will help keep levels of severe disease low even as cases rise.

Jenny Harries, chief executive of Britain’s Health Security Agency, earlier called the Omicron variant “probably the most significant threat” since the start of the pandemic.

“The numbers that we see on data over the next few days will be quite staggering compared to the rate of growth that we’ve seen in cases for previous variants,” she told a parliamentary committee.

Ms Harries said that Omicron had the potential to put the National Health Service “in serious peril” because of the speed at which infections were increasing.

-AAP