If you notice an extra buzz from your favourite wine...

Some wine contains more alcohol than manufacturers claim, researchers in the US have found. Photo / iStock

If you are struggling with a hangover tomorrow morning, it might not be entirely your own fault.

Wine contains more alcohol than manufacturers claim, putting health at risk and increasing drivers' chances of being over the limit.

Academics at the University of California, Davis took samples from nearly 100,000 bottles of wine across the world and discovered that the alcohol content in nearly 60 per cent was an average of 0.42 per cent higher than that stated on the label.

And it appears that winemakers are aware of the discrepancy, admitting to researchers that they alter the percentage to meet drinkers' expectations of alcohol strength.

Chilean and Spanish reds had the biggest margin of error between the percentage of alcohol stated on the bottle and the actual content. Chilean and American whites were also among the worst offenders.

"A discrepancy of 0.4 percentage points might not seem large relative to an actual value of 13.6 per cent alcohol by volume, but even errors of this magnitude could lead consumers to underestimate the amount of alcohol they have consumed in ways that could have some consequences for their health and driving safety," said lead author Professor Julian Alston, of the Department of Agricultural and Resource Economics at UC Davis.

In some instances, the discrepancies could be much larger than average, according to the research published in the Journal of Wine Economics.

"For instance, Napa Valley Cabernet might be expected to have alcohol content within the range of 13.5-14.5 per cent alcohol by volume, and an average error of 0.4 percentage points is large in the context of this range," he said.

Researchers said they found a "tendency to overstate the alcohol content for wine that has relatively low actual alcohol, and a tendency to understate the alcohol content for wine that has relatively high alcohol content".

Alcohol Concern, the British charity, called on the Government to do more to stop the practice. Tom Smith, director of campaigns, said: "We need the Government to ensure accurate health warnings on alcohol products are made mandatory, as is standard practice in other countries.

"The public should be able to make informed choices about their health and drinkers have a right to know what they're consuming."