LONDON — The British government estimates that 200,000 people a day are being infected with the latest coronavirus variant, Omicron. Yet in Parliament on Tuesday, a record number of Conservative lawmakers voted against one of Prime Minister Boris Johnson’s key measures to quell the outbreak, a policy of vaccine certification to enter nightclubs and places with large crowds.
The policy passed, with the help of votes from the opposition, as did several other related Covid measures. But with nearly 100 Conservatives voting against Mr. Johnson, it was a stinging rebuke of their leader, undermining his authority at a time when he has called for a national campaign to prevent Omicron from swamping the country.
There are various explanations for this paradox, ranging from Britain’s cherished tradition of protecting individual liberties to a deep sense of fatigue with a government that has lurched from policy to policy during the pandemic, reversing itself and exhibiting a tendency to flout the rules it imposes on others.
Whatever the reasons, the striking parliamentary mutiny leaves Britain in a curious place as it battles the latest wave of the virus: mobilizing a national vaccine booster campaign, while clinging to the vestiges of the live-and-let-live approach it used last summer, when Mr. Johnson threw off most restrictions in England in what became known as “freedom day.”
The rebellion among Conservative lawmakers — the worst since Mr. Johnson won a landslide election victory in 2019 — is an acute embarrassment for him and attests to his debilitated political standing in the wake of disclosures that his staff held a Christmas party last December, at a time when the government was instructing the public not to attend such gatherings.
“The Omicron wave is colliding with growing skepticism among Conservative members of Parliament that further restrictions are necessary,” said Matthew Goodwin, a professor of politics at the University of Kent.
While there has long been a committed band of lockdown-skeptics in the Conservative ranks, he said, these insurgents have now allied with lawmakers who simply believe the government’s Plan B will have little effect in curbing a variant that is causing infections to double every two to three days.
“The events in Parliament are symbolic not only of a changing mood within the Conservative parliamentary party,” Professor Goodwin said, “but also symbolize a growing electoral problem for Johnson.”
Nearly 40 Conservatives also voted against the government’s plan to expand the compulsory use of face masks — a significant number of defections, though not a threat in a chamber where Mr. Johnson’s party holds an 80-seat majority.
But the rebellion turned into a mutiny when voting began on what Mr. Johnson calls a “Covid certification” policy and what critics describe as “vaccine passports.” This would require people entering nightclubs, large indoor venues and some sporting events in England to show proof of vaccine status or of a recent negative Covid test.
Defenders of vaccine passes say they have driven up vaccination rates in France and Italy, where they are widely used. But they have also ignited protests in both countries, with critics calling them discriminatory.
In Britain, libertarians have reacted with outrage, invoking fraught, if familiar, historical analogies. “This is not Nazi Germany,” one Conservative lawmaker, Marcus Fysh, told the BBC. “It’s the thin end of an authoritarian wedge.”
Graham Brady, chairman of the influential 1922 committee of Conservative backbenchers, described Mr. Johnson’s plan in the Daily Telegraph as “the government’s latest authoritarian nonsense” and a “disastrous assault on liberty.”
Other lawmakers argue that Covid certificates have been ineffective in other countries that have tried them, including Scotland, and will have a disastrous impact on the economy. “‘Just in case’ isn’t good enough to destroy more jobs and lives,” Craig Mackinlay, a Conservative lawmaker, wrote on Twitter.
With support from the Labour Party and other opposition parties, the measure still passed by a vote of 369 to 126.
For public health experts, Mr. Johnson’s weakened political standing has dire epidemiological implications. Devi Sridhar, head of the global public health program at the University of Edinburgh, said it was “politically difficult for the PM now to have any authority to put in place necessary protections.”
Even if Omicron is less severe than other variants as some early research indicates, Professor Sridhar said, it will still cause significant economic disruption since people who are infected would have to isolate at home for seven to 10 days.
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On Tuesday, the government relaxed one restriction, removing 11 countries from its “red list,” which requires travelers to quarantine in a hotel after they arrive in Britain. The decision, which applies to Botswana, South Africa and nine other African countries where Omicron surfaced early on, essentially acknowledges that the variant is now so widely found that the restrictions no longer matter.
Legal experts drew a distinction between the measures the government is imposing now and the lockdowns it imposed earlier in the pandemic. Britain is mainly tightening rules to encourage more people to get fully vaccinated. Mr. Johnson even floated the idea of compulsory vaccinations to address the roughly 30 percent of the population that has yet to get inoculated.
“I don’t think that mandatory vaccinations are likely to happen, but by raising the possibility, the government is signaling again that its long-term strategy relies on vaccinations, not lockdowns,” said Adam Wagner, a London-based human rights lawyer and expert on Covid-related laws.
“The government had hoped that the ‘wall of vaccination’ was the way to break the connection between rising cases and hospital admissions,” Mr. Wagner said, “and that has worked since the summer. But it has also always said that a new variant could change the dynamic. Omicron may do that.”
Behind the revolt lie shifting political currents that could pose a significant threat to Mr. Johnson. The Tories have fallen behind Labour in opinion polls and face a new challenge on their right from Reform UK, a party that emerged from the ashes of the Brexit Party and opposes lockdown measures.
Brexit-supporting lawmakers from the north of England are frustrated over the lack of substance behind the government’s promise to “level up” the country and bring prosperity to the regions they represent.
Others are angry at the ethical cloud hanging over Downing Street because of an inquiry into reports it held Christmas parties last year and an investigation into the funding of Mr. Johnson’s refurbishment of his apartment. There are also allies of the former prime minister, Theresa May, who are hostile to Mr. Johnson because he purged many of their colleagues before the last election.
“Johnson has successfully alienated different wings of his party,” Professor Goodwin said.