The Houses of Parliament has said it will not serve alcohol on its premises after 10pm despite not being subject to England's Covid-19 hospitality curfew.
Parliament is not bound by the early closing time because of exemptions for "workplace canteens" where there are no "practical" food alternatives on offer.
While most of its bars remain shut, MPs said the rules risked making Parliament look "ridiculous" to the public.
Food will still be available after hours when Parliament is sitting late.
A spokesman said no alcohol had been served in any of its facilities in the House of Commons and the Lords since the new restrictions came into force last week.
The parliamentary authorities said catering facilities would remain open "in line with the government's industry guidance… to serve food for those still working and to support social distancing".
Since Thursday 24 September, all pubs, bars, restaurants and other hospitality venues in England selling food and drink have been required to close at 22:00 BST, except for takeaways, to help curb the spread of coronavirus.
A small number of venues are exempt from the rules, including canteens at hospitals, prisons, army bases and homeless shelters.
Under the rules, "workplace canteens" can also stay open if it is deemed "there is no practical alternative for staff at that workplace to obtain food".
News that Parliament was not legally bound by the same rules as hospitality businesses across England, first reported by The Times Red Box, was met by criticism from MPs.
Labour's Wes Streeting said the situation "had to change immediately" while Conservative George Freeman said it risked bringing Parliament "into disrepute".
In response, the Parliamentary authorities said Commons Speaker Sir Lindsay Hoyle had taken the decision on Thursday, when the new 10pm limit came in, that Parliament must abide by it in relation to alcohol.
It said no alcohol had been served on the Parliamentary estate since the guidelines came in but that Monday would be the first day that it would take practical effect, with the Commons likely to sit after 10pm.
MPs will debate the curfew and other coronavirus restrictions later on Monday amid growing unease among many Conservatives about their effectiveness and economic impact.
Conservative MP Tim Loughton pointed out most of the bars had been shut since the outbreak began in March, tweeting that "we have more restrictions than the public at large".
Parliament is exempt the same as all royal palaces. However the bars have been closed completely since March anyway so we have more restrictions than the public at large. We are exempt from the smoking ban for example but brought it in ourselves anyway as with most other laws. https://t.co/arsezfU4mi— Tim Loughton MP #StayAlertSaveLives (@timloughton) September 28, 2020
There are multiple bars and restaurants in the Palace of Westminster, which is situated in central London, for the use of MPs, peers, staff and other passholders.
They include the Adjournment, Churchill Dining Room, Members Dispense Bar, Press Bar, Pugin, Strangers Bar and Moncrieffs. They have traditionally stayed open late to accommodate evening parliamentary sittings.