The amount of alcohol consumed in England could be much higher than previously thought, a study suggests.
University College London researchers compared alcohol sales figures with surveys of what people said they drank.
They found there was a significant shortfall with almost half of the alcohol sold unaccounted for in the consumption figures given by drinkers.
This suggests as many as three-quarters of people may be drinking above the recommended daily alcohol limit.
The researchers reached their estimates by factoring in the "missing" alcohol - and found excess drinking was far more than suggested by official figures, they told European Journal of Public Health.
Experts said much alcohol use went unreported, partly because drinkers did not admit or keep track of how much they consumed.
The study found that 19% more men than previously thought were regularly exceeding their recommend daily limit - and 26% more women.
Total consumption across the week was also higher than officially thought - with 15% more men, and 11% more women drinking above the weekly guidelines.
The current recommendation set by the UK Chief Medical Officers is not to regularly exceed four units per day for men and three units a day for women; the Royal College of Physicians recommends weekly alcohol limits of 21 units for men and 14 units for women - although these are currently under review.
A unit of alcohol is roughly equivalent to half a pint of ordinary strength beer, or nearly one small (125ml) glass of wine.
Sadie Boniface, lead author of the study at University College, said: "Currently we don't know who consumes almost half of all alcohol in England. This study was conducted to show what alcohol consumption would look like when all of what is sold is accounted for, if everyone under-reported equally.
"The results are putative, but they show that this gap between what is seen in the surveys and sales potentially has enormous implications for public health in England."
The team used alcohol sales data from Revenue and Customs and compared it with two self-reporting alcohol consumption surveys conducted in 2008 - the General Lifestyle Survey (GLF) which analysed average weekly alcohol consumption in 12,490 adults, and the Health Survey for England (HSE) which looked at consumption on the heaviest drinking day in the previous week among 9,608 adults.
The researchers say they will now look at the characteristics of those that are under-reporting the number of drinks they have had, and why.
They suggest it may be down to drinking patterns and habits - those that are mixing drinks, and drinking at different venues, may be more likely to under-report.
The charity Alcohol Concern suggests irregular and chaotic drinking behaviour may play a part: "When we're totting up our drinks total we don't always count some occasions as proper drinking.
"We may underestimate drink sizes and their alcoholic content, and not count holidays and special occasions like weddings, birthdays and Christmas when we often drink a great deal more than usual."
The researchers suggest that government drinking guidelines need to reflect actual consumption instead of reported drinking - especially when ascertaining what levels are associated with harm.
The Department of Health says this will be taken into consideration in their alcohol consumption review.
It said: "We already know people underestimate what they drink and many drink too much. That's why we work to help people make healthier decisions, including the recent Change For Life campaign to help them track consumption and understand the impact on their health.
"We're also tackling excessive drinking through our proposed minimum unit price at 45p per unit, tougher licensing laws, more GP risk assessments, better access to specialist nurses and more specialised treatment."
Diane Abbott MP, Labour's shadow public health minister, said: "This has got to be a wake-up call for the government and the country, because after more than two years of bitter internal rows, the government has got cold feet about its only proposed alcohol harm policy.
"More needs to be done to tackle problem drinking, which costs the country £21bn."