The prime minister told MPs on Wednesday that the legal requirement to self-isolate could be scrapped by the end of this month, instead of at the end of March as originally planned.
But the move has been met with unease by the scientific community, with national Covid cases once again on the rise.
Mr Johnson was accused of playing “fast and loose with people’s health” in an attempt to placate restive Tory backbenchers as the fallout from Partygate continues.
Labour’s West Streeting, the shadow health secretary, said the announcement at the start of PMQs was “designed to dig [the prime minister] out of a political hole, with no plan to back it up”.
As well as ending the legal requirement to isolate, legal powers for councils to shut down premises linked to outbreaks will be removed. But no changes are expected to international travel restrictions, and the supply of testing kits free of charge will continue, said Mr Johnson’s official spokesperson.
One member of the government’s Scientific Advisory Group for Emergencies (Sage) said that no consideration had been given to the prospect of lifting self-isolation rules during the most recent meeting.
Another scientific adviser to the government said the PM’s announcement “doesn’t seem very cautious”, adding that he was “very concerned that the number of cases remains very high”.
Dr Simon Clarke, an associate professor in cellular microbiology at the University of Reading, called the move “an experiment which will either be shown to be very brave or very stupid – but nobody knows for sure what the result will be”.
Guidance will remain in place to stay home after a positive Covid test – as with any infectious disease – but it will not be legally enforceable. No 10 declined to say whether the £500 support payment for those isolating would be withdrawn.
“Provided the current encouraging trends in the data continue, it is my expectation that we will be able to end the last domestic restrictions – including the legal requirement to self-isolate if you test positive – a full month early,” the PM said.
He said he would present the government’s “Living With Covid” strategy when the Commons returned from recess on 21 February. Aides said remaining restrictions were expected to be lifted by 24 February at the latest.
The surprise policy announcement came as new figures from the Office for National Statistics (ONS) figures showed infection levels had risen in most parts of the UK, with only Wales experiencing a clear week-on-week decline.
In England, around one in 19 people was estimated to have had the virus in the week to 5 February, equating to 2.8 million people – up from one in 20 in the previous week. However, the ONS described the trend as “uncertain”.
Paul Hunter, a professor in medicine at the University of East Anglia, said he “certainly didn’t expect” the government to drop its self-isolation guidance this month.
He said there were “grounds for optimism” in the current data, pointing to the example of falling cases among children and declining hospital admission rates, but expressed concern over those who are clinically vulnerable, saying: “There need to be robust procedures in place to ensure infections in this group are diagnosed early and antivirals are provided within hours of any positive result.”
Professor Peter Openshaw, a member of Nervtag, a subcommittee of Sage, told BBC Radio 4 that “it would be wholly wrong to say that the pandemic is in any way over”, and suggested that the population had “become rather used” to the country’s high infection and death rates.
On Wednesday, 68,214 new cases were reported, along with 276 further deaths and 1,196 hospitalisations.
“I think we’re all really looking forward to being able to get back to some sort of normality, and we know Omicron is generally fairly mild in people who have immunity, and most adults have immunity now, either because we’ve been vaccinated or because we’ve been infected or both.