Nearly half of young men under 25 are binge-drinking when they go on a night out - as are more than a third of women in the same age group - according to a survey.
Most do not keep track of what they drink and insist they are not binge-drinkers. Many think it will have no effect on their health.
Overall, a quarter of adults are involved in bingeing sessions, with one in three men and one in five women drinking at least double maximum recommended daily intakes on such evenings. Two thousand people were interviewed in August for Bupa Wellness, part of the private health group, with questions focusing on bingeing sessions.
The government's definition of binge drinking is one in which women drink, in a short time, at least six units - three glasses of wine or six spirit measures.
It is eight units, four pints of beer or eight spirit measures, for men.
The latest warning, with the suggestion 47% of young men and 35% of young women are bingeing, is published less than a month before licensing laws allow more flexible pub opening, a move critics fear will make things worse.
However ministers, who yesterday met supermarket representatives over a plan to crack down on underage drinkers by ensuring under-18s are not sold alcohol, insist extended police powers should mean less drink-related disorder.
Eight in 10 people in the Bupa survey said they did not keep track of how much they drank while out and a defiant one in six thought longer opening hours would help them drink more. At least one "hangover" day off work a year was admitted by 15%, with some taking up to five days.
Peter Mace, medical director of Bupa Wellness, said: "Drinking limits are not as easily defined as they once were. There is no such thing as a standard drink any more.
"A pint of beer or glass of wine is served in a variety of strengths and sizes so it's confusing for people to know exactly how much is safe to drink.
"What is clear is that people who storm the bars or who drink excessively at home on a regular basis will face serious health issues in the years to come."
People were not asked about their normal drinking habits during a week or year. The Portman Group, the industry-funded body promoting "responsible drinking", recently revealed one in three young women said they had been sexually assaulted after getting drunk on a night out and women were more likely to be involved in fights, arrested or cautioned by police.
Kate Winstanley, the Portman policy director, said the Bupa figures were worrying and credible.
"Industry is doing its bit. We have persuaded all our member companies and many others to unit label products." These reflected increased alcohol strengths.
The group also ran a Drink Aware website. "When you can go and buy as much as you want and drink it in your sitting room, there does need to be an element of personal responsibility."
Solicitor Philip Hyde, author of a new book, Local Authority Alcohol and Entertainment Licensing, suggested new powers could actually shorten pub hours in town centres.
"Entertainment districts like Soho (and similar districts up and down the country) which have a central role in our tourism industry, rather than being given a fresh lease of life, could actually be stifled by local authorities with nimbyist tendencies."
