The UK recorded 78,610 new COVID-19 cases on Wednesday – its largest number of daily infections since the start of the pandemic and about 10,000 more than the previous high reported in January.
More than 11 million people have now tested positive for the disease in the UK, which has a total population of around 67 million.
A senior British health chief said there could be a "staggering" rise over the next few days.
The news came on the day tough new anti-coronavirus measures came into effect in England, despite a major rebellion within the ruling Conservative Party, with many defying Prime Minister Boris Johnson and voting against the new rules.
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Johnson's authority has been badly eroded in recent weeks with a series of political missteps and scandals. He is regarded as a brilliant campaigner who two years ago won one of the largest majorities his party has enjoyed in decades – an 80-seat majority in the House of Commons.
But public anger at his recent problems has unnerved many Conservatives who now feel willing to rebel on issues they don't agree with, such as how to deal with the rise of the Omicron variant of COVID-19.
Long lines continue to form outside vaccination centers as people rush to get a third dose, or booster, of vaccine against the coronavirus. The government has set a target of getting everyone eligible boosted by the end of the year, placing a huge strain on the health service.
People wait in line to get a booster dose of COVID-19 vaccine at Smallthorne Community Centre in Stoke-on-Trent, Britain. /Reuters/Carl Recine
The authorities are concerned Omicron is proving more contagious than previous variants. In an interview Wednesday morning, Transport Secretary Grant Shapps warned about the speed with which it is spreading.
"It's doubling every two to three days, which is incredibly fast, and the thing about doubling rates like that is you can go from seemingly almost nothing, of course, to suddenly it becoming a thing that overwhelms you," Shapps warned.
Now in a further bid to slow the spread of the virus, "vaccine passports" or proof of a negative test are needed for nightclubs and big sporting and other events. This came into effect on Wednesday following Tuesday's vote in parliament
Also, anyone working in the National Health Service or care homes must now be vaccinated.
The Omicron variant (red line) has spread at a far faster rate during the first weeks of its discovery in England than did the Delta variant (blue line).
But getting these measures through parliament was not easy as almost a hundred Conservative lawmakers defied Johnson and voted against the COVID-19 passports.
Much to the government's embarrassment, it took the opposition Labour Party's support to get the measures passed.
Tuesday evening's vote is the latest blow to Johnson, who has faced weeks of bad press over allegations of sleaze and holding Christmas parties last year during lockdown when such gatherings were illegal. An official investigation is now under way.
There were heated exchanges at Prime Minister's Questions on Wednesday, with the opposition Labour leader Keir Starmer making the most of the splits in the ruling Conservative Party.
"The Labour Party showed the leadership yesterday what the prime minister lacked," Starmer said. Adding: "So weak is his leadership, his own MPs were wrong to vote against public health measures."
Not to be outdone, Johnson turned the tables on his opposite number: "There he goes again. He comes to this House pompously claiming that he wants to rise above our party politics and support the efforts of the nation in delivering the vaccine roll-out. Then he plays party political games…
"I think the public can see what we have done in delivering the fastest vaccine roll-out in Europe and now the fastest booster roll-out."
Whitchurch in the North Shropshire constituency in central England, which usually elects a Conservative MP by a large majority, but could provide an upset for Boris Johnson. /Paul Ellis / AFP
The next big test for Johnson comes on Thursday with a by-election in the West Midlands county of Shropshire. This has long been a Conservative stronghold but the previous member of parliament resigned in disgrace and the result is far from certain.
It's a big if, but were the Conservatives to lose their 23,000 majority in the seat and an opposition candidate to win, then we could see Johnson facing a leadership challenge before too long.
It's far from certain but the Conservative Party is famously ruthless if it feels a leader has become an electoral liability.
Cover photo: A person wearing a protective face masks walks past the Elizabeth Tower, more commonly known as Big Ben, in London, Britain, December 15, 2021. /Reuters/Henry Nicholls