(Telegraph) - If you are struggling with a hangover this morning, it might not be entirely your own fault.

Wine has more alcohol in than manufacturers claim, putting drinkers’ health at risk and raising the chance of being over the drink-driving limit.

Academics at the University of California 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 stated on the label.

And it appears that winemakers are entirely aware of the discrepancy. They admitted to the researchers that they alter the percentage to meet customers’ expectations of how strong a bottle of alcohol should be.

Overall the study showed that Chilean and Spanish reds had the biggest margin of error between what percentage is stated on the bottle and what the wine actually contains. Chilean and American white wine 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 the University of California Davis.

“In particular instances the discrepancies could be much larger than average.

“An average error of 0.4 percentage points is much more significant compared with the typical range for wines in a particular category, 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."