An estimated 2.3 million people in the UK had COVID in the week up to 23 December – a substantial rise on the 1.4 million the previous week.
It is the highest number since comparable figures began in autumn 2020, the Office for National Statistics said.
In London, around one in 15 people was likely to test positive for COVID in the week to 23 December, the highest proportion for any region in England.
Infection rates increased across all four UK nations, with one in 25 in England estimated to have had COVID.
The rate was one in 40 for Wales, Northern Ireland and Scotland.
England and Scotland’s rates are the highest since records began.
All figures are for people in private households.
Professor Paul Hunter, an expert of infections diseases at University of East Anglia, told Sky News that “a high peak now probably means that by the end of January we will be seeing relatively few cases compared to what we are seeing at the moment”.
He added: “So it’s a difficult choice: do we have the high peak of infections now and the pressure that that is undoubtedly bringing on the health service or do we try and suppress that but extend the duration that the NHS is under pressure as new cases arrive?
“We know any infectious disease that spreads really quickly reaches its peak very early, a high peak, and then generally falls quite rapidly at the other side.
“There is hope that it would peak and fall quickly. I don’t think it’s a forlorn hope. But certainly I don’t think we can guarantee that that would happen.”