Drinks companies should label alcoholic products to show the number of calories they contain as part of a bid to tackle obesity, a health organisation has said.

Irresponsible drinking is causing an obesity epidemic and threatening public health, the Royal Society for Public Health (RSPH) said.

In a paper highlighting the "invisible" calories in alcohol, the organisation called for calorie counts to be included alongside the number of units, daily guidelines advice and pregnancy warnings, which drinks companies agreed to include on packaging as part of a deal with the Government in 2011.

The move was backed by Alcohol Concern but drinks producers said the laws required could take years and people should be more focused on alcohol content.

RSPH chief executive Shirley Cramer said: "Calorie labelling has been successfully introduced for a wide range of food products and there is now a clear public appetite for this information to be extended to alcohol to help individuals make informed choices.

"With two in three adults overweight or obese, and given that adults who drink get approximately 10 per cent of their calories from alcohol, this move could make a major difference to waistlines of the nation."

The RSPH has urged the labelling change to be brought in throughout the EU.