Boris Johnson has been challenged to publish the scientific evidence behind the 10pm closing time for English pubs ahead of a vote by MPs next week.
Labour leader Sir Keir Starmer said the public “deserved to know” the basis for the restriction and if it could not be justified the rule must be reviewed.
Tory MPs opposed to the move may rebel in the Commons vote.
The PM said the rationale behind it had not changed and it was designed to reduce the spread of the virus.
The two party leaders clashed over the effectiveness of national and local Covid restrictions at Prime Minister’s Questions, with Sir Keir accusing the PM of incompetence and the PM saying Labour had supported the government’s position, then changed its stance.
All pubs, bars, restaurants and other hospitality venues in England have been required to close at 10pm since 24 September, as part of a package of measures to try and contain a surge of new cases in the North of England.
Ministers argue it has had a “beneficial effect” on the spread of the virus in areas where the restriction had already been tried – but it has become a lighting rod for dissatisfaction on the Tory benches about Covid restrictions.
And regional leaders, including the mayors of Manchester and London, have called for it to be reviewed amid concerns it has led to large crowds gathering outside venues in some cities after closing time.
Meanwhile, pub operator Greene King has announced it will shut dozens of pubs with the loss of 800 jobs.
The company said it will keep 79 of its sites shut for the time being, with around one third of these closures expected to be permanent.
Evidence for regulations
Sir Keir said there were “deeply-held views” about the curfew issue all over the country and MPs, who will vote on whether to keep the regulations in force on Monday, needed to know the evidence for how it reduced transmission.
He said: “One question is now screaming out. Is there a scientific basis for the 10pm rule? The public and Parliament deserve to know. If there is, why does the government do itself a favour and publish it?
“If not, why does the government not review the rule?”
In response, Mr Johnson suggested Labour could not make its mind up whether existing restrictions were too strong or not strong enough.
“The basis on which we set out the curtailment of hospitality was the basis on which he accepted it two weeks ago and that is the reduce the spread of the virus and that is our objective,” he said.
The PM accused Labour of withdrawing its support for other restrictions, after its MPs were told to abstain in a vote on Tuesday on maintaining the rule of six limit on social gatherings.
“What kind of signal does this send to the people of the country,” he added.