Keir Starmer has called on the government to publish the "scientific basis" for the 10pm hospitality curfew before MPs are due to vote on it next week.
The Labour leader questioned the effectiveness of the measure, which came in to force on 24 September, at Prime Minister's Questions on Wednesday.
If Labour opposes the motion, which Starmer said would be put to a vote on Monday, it could see the curfew overturned with 'dozens' of rebel Conservatives preparing to defy the whip to vote down the government.
Starmer said: "One question is now screaming out, is there a scientific basis for the 10pm rule?
"The public deserves to know; parliament deserves to know. If there is, why doesn't the government do itself a favour and publish it?
"If not, why doesn't the government review the rule?"
A vote on the curfew was originally due to take place this week but has been pushed back amid reports of a backbench Tory revolt.
Boris Johnson said: "The basis on which we set out the curtailment of hospitality was the basis on which [Starmer] accepted it two weeks ago. That is to reduce the spread of the virus.
"That's why we introduced the rule of six.
"We are taking the tough decisions that are necessary, that we don't want to do, but imposing restrictions locally and nationally to fight the virus, keep kids in education and keep the bilk of our economy moving."
Backlash against the curfew is building and a legal challenge has been launched demanding the release of the scientific advice behind the cut-off time.
The Caterer has launched a petition calling on the government to scrap the curfew. To sign click here.