LONDON—The British have famously strict etiquette for queuing. Dare cut in line here and you’ll quickly be met with scorn, or at least a tut. But there is one place where forming a single line has long been frowned upon: the pub.

For centuries, getting a drink in Britain has meant going straight to the bar, finding a gap and making eye contact with the bartender. No more.

More people are now ordering their pints from single-file lines, and it’s driving pub purists to distraction.

“As British people, we absolutely love queuing. But the one place that we’ve never really done that is the pub,” said Kelly Maxwell, who manages Neepsend Social Club & Canteen in Sheffield, England. “It makes it so long and tedious.”

She recently put up a new sign: Please stand at the bar.

The sign at Glasgow’s Drury Street Bar & Kitchen is less polite. “Stop f— queuing! Elbows on the bar!,” it told drinkers. The dive bar says it “will not rest until the problem is eradicated.”

Neither will QueuesPub , the social-media account launched in 2022 to chronicle this emerging faux pas—and try to end it.

Behind the campaign is an unlikely hero: schoolteacher Rod Truan. He was struck with the idea after seeing people line up single file at a pub in Cornwall. The queue felt a “bit weird, not normal and certainly no way to behave.”

Concerned citizens send photos of the queues they’ve witnessed to Truan, who then posts them and the pub, named and shamed. He says the campaign is working; he has overheard people warning others to “get to the bar or you will end up on that account.”

On a recent day, a long single-file queue spilled outside the Rutland Arms in west London, aggravating bartender Lauren Hodgins.

“It’s so inconvenient,” she said. “It means we have to repeatedly yell ‘Who’s next?!’ trying to get the attention of whoever thinks they’re at the front of this queue—and half the time, no one even responds.”

Occasionally, Hodgins says, someone breaks rank and goes straight to the bar. They might get a mouthful from someone who’s been queuing for the past 20 minutes, but they will always get immediately served.

“It’s a pub, not the women’s toilets,” Hodgins said. “I know this is England, but please stop queuing.”

The trouble started during the pandemic , when lining up a few feet apart was a temporary requirement taken to protect pubgoers. Three years after social distancing ended, single-file queues still form.

The culprits? Most hardened pubgoers blame Gen Z.

Having come of age around social distancing, zoomers have continued the practice. Some younger pubgoers say it ensures fairness, instead of the old informal system where bar staff must keep tabs on who has been waiting longer.

“The whole single-file queue thing feels way more civil and respectful,” said Ahona Das, a student in London. “No one’s being rude, everyone respects each other’s space, and eventually everyone gets their drink when it’s their turn.”

Gen Z isn’t alone in the habit. It is especially “weird how pub drinkers of 30 years’ experience are caught doing it,” Truan says.

But for many older patrons, a single-file queue makes the pub feel sterile, like a supermarket checkout or passport control. The scrum at the bar is a key—and joyful—part of pub culture.

“Pubs have 40-foot-long bars for a reason: To chat and socialize,” said Truan.

People standing in a single-file line are far less likely to strike up a conversation with a stranger, he adds. Most just stare into their phones.

British pubs are a ritualized, almost sacred space, says Thomas Thurnell-Read, a lecturer in sociology at Loughborough University who has conducted several studies of British drinking culture.

Many younger people don’t revere the pub in the same way as previous generations, he says. Four in five zoomers would prefer to visit pubs with karaoke, games, themed events and live music, over the traditional offering of Sunday lunch and beer, according to a 2024 pub consumer survey .

They are also—cue the older generations shaking their heads in dismay— drinking less . In 2024, one in five 18- to 34-year-olds in the U.K. said they didn’t drink any alcohol.

It all feeds into a broader anxiety about a decline in pub culture , said Thurnell-Read, especially so-called proper boozers where bartenders know their clients’ orders by heart. Nearly 300 pubs closed across England and Wales in 2024—an equivalent of six a week—according to the British Beer and Pub Association.

Pub staff worry single-file queues could add to the problem, discouraging people from coming in for a pint.

Still, the pub queue—and debate over it—show no sign of abating. On a recent Wednesday evening, Daniel Gilbody, a middle-aged executive, was enjoying a pint with his buddy Peter Smolen outside a London pub.

Asked about single-file queues, they struck up a discussion. Gilbody favored the “law of the jungle.” Smolen disagreed, saying the traditional system only works if the bar staff are skilled enough. But with London’s pubs understaffed, he said, there was “a lack of order.”

The discussion went on for half an hour until Smolen turned to a reporter and said, “You probably have enough material by now.”

Write to Roya Shahidi at roya.shahidi@wsj.com