Parliament has said it will not serve alcohol after the 10pm curfew, after it emerged its bars and restaurants would remain open due to an exemption in Boris Johnson's coronavirus rules.
The strict deadline for England's hostelries has been criticised by businesses and raised concerns it may do more harm than good by forcing crowds into the streets at the same time.
But the law came under fresh scrutiny when it was disclosed that MPs, Lords and parliamentary staff would be able to continue drinking past the deadline in the Palace of Westminster, because its establishments are classed as workplace canteens.
The regulations announced by the Prime Minister last week include exemptions that "workplace canteens may remain open where there is no practical alternative for staff at that workplace to obtain food".
But after the decision to keep the bars open came in for cross-party criticism, Parliament announced a U-turn with immediate effect.
A spokesman said: "Alcohol will not be sold after 10pm anywhere on the parliamentary estate."
Catering facilities will, however, continue to serve food after the deadline when the House is sitting.
Despite being in the centre of London there are relatively few shops surrounding Parliament, particularly ones open late at night, and politicians and staff tend to eat on site.
Health Minister Helen Whately had said she had been unaware that the curfew did not apply to Parliament and seemed unimpressed.
"We in Parliament shouldn't be sitting round late at night drinking. We have got a job to do when we are there," she told BBC Radio 4's Today programme.
Senior Conservative backbencher Steve Baker was also critical, and anticipated it would be changed.
"This surely will not last the day, and rightly so," he said.
The SNP's Ronnie Cowan tweeted: "One rule for the public and another for Westminster (sounds familiar)."
The curfew, which came into force on Thursday, has proved controversial, with businesses warning their profitability will be jeopardised and police struggling to disperse large crowds forming after the deadline on Saturday night.
Greater Manchester mayor Andy Burnham has also warned it may be doing "more harm than good", with people piling on to public transport and queuing outside shops to buy more alcohol.