Five bars have been caught selling alcohol to underage teenagers in what police have called a “widespread” problem.
The test purchase operation saw 17-year-old police cadets sent into pubs, bars and clubs across Brighton and Hove.
The venues which served them were Synergy, in Middle Street, The Royal Pavilion Tavern, in Castle Square, The Haunt, in Pool Valley, The Fishbowl, in East Street and Molly Malone's, in West Street.
Police bosses are now considering asking for their licences to be stripped following new strict government guidance.
Jean Irving, Sussex Police licensing and public safety manager, said: "We thought there was an issue with a few premises in the city who we had received intelligence about, which indicated they knew they were selling drink to children and didn't seem to care.
"This operation has made us very concerned that this isn't an isolated problem but a widespread one in the city.”
During the operation only two of the five venues asked the 17-year-olds for ID. They were allowed in even after telling door staff they did not have any.
Once inside all venues sold the teenagers alcohol.
The management in each venue blamed the door staff despite all committing to a two-stage defence against underage drinkers - the door staff first but then the bar staff second.
As well as the threat of the venues losing their licence, bar staff were issued with £90 on the spot fines.
Officers are also looking into the possibility that during the operation door staff at some venues tipped off others that licensing officers were testing pubs, clubs and bars.
Chief Inspector Katy Woolford said: "These are very disappointing results which indicate there is a lot of work still to do with a number of venues that are willing to sell alcohol to children.
"They have a duty of care to keep people safe, particularly the vulnerable such as children, which is clearly not the case in these five instances."
As part of the operation on Friday, officers also checked venues which had previously been caught selling alcohol to underage punters.
However, Wahoo, in West Street, The Funfair Club, in Kings Road, and Al Nakhl, in West Street, all asked to see ID when teenage police cadets tried to go in and refused to serve them alcohol.