An estimated 3.7 million people in the UK had COVID-19 in the last week of the year, the Office for National Statistics has said.
The figure for the week ending 31 December was up from 2.3 million in the week to 23 December. It marked the highest number since comparable figures began in autumn 2020.
According to the latest ONS infection survey, an estimated one in 15 people in England had COVID in the week up to 31 December.
This is the equivalent to 3,270,800 people.
In Scotland and Wales, an estimated one in 20 people had the virus, while in Northern Ireland the figure was one in 25.
It comes as a record number of daily COVID cases – more than 218,000 – were recorded in the UK on Tuesday, with the highly transmissible Omicron now the dominant strain in the country.
However the reporting of some of those cases had been delayed due to a lag over the festive period.
Meanwhile, Boris Johnson has led a Cabinet meeting where he recommended sticking with England’s Plan B despite the record infection numbers and increasing pressure on hospitals.
The Plan B measures, which will be reviewed before they are due to expire on 26 January, include work-from-home guidance, mask-wearing and COVID health passes.
At a news conference on Tuesday, the prime minister argued the vaccine booster rollout has given people substantial protection and claimed: “We have a chance to ride out this Omicron wave without shutting down our country once again.”
Mr Johnson accepted the coming weeks were going to be “challenging” and said “some services will be disrupted by staff absences” as he pledged to “fortify” the NHS to withstand the pressures and protect supply chains.
And in the Commons on Wednesday, the PM said “this will unquestionably be a difficult period for people”.
Also, people in England who test positive on lateral flows will no longer need a follow-up PCR to begin their isolation period if they do not have symptoms, the UK Health Security Agency has confirmed.
In Scotland, Nicola Sturgeon has announced the coronavirus isolation period is to be reduced from 10 days to seven.
The change comes into effect from midnight and brings the nation broadly in line with the rest of the UK.
People will be able to leave their isolation after seven days provided they test negative on lateral flow tests for the last two days and have no fever.
They will be asked to take a lateral flow test no earlier than day six and a second test at least 24 hours later.