The new label shows daily alcohol limits for "responsible drinkers"

The warnings will appear on Scottish & Newcastle's Newcastle Brown ale, extending next year to brands such as Fosters, Kronenbourg and John Smith's.

There will also be details of a new website - drinkaware.co.uk - that enables people to compare their alcohol intake with government guidelines.

Other brewers are expected to follow Scottish & Newcastle's move.

Coors, which brews Carling and Grolsch lagers, has said it will introduce a similar policy next year.

SAFE DRINKING GUIDELINES One 175ml glass of normal wine (12%) = 2 units One pint of normal strength lager (3.5%) = 2 units A single (25ml) measure of spirits (40%) = 1 unit Men are advised to drink no more than four units a day Women are advised to drink no more than three units a day Two to three alcohol-free days a week are also recommended

The labels on Scottish & Newcastle's Scottish Courage brands explain that responsible drinkers should not exceed four units of alcohol a day for men and three for women.

Drinkers will also be told how many units are in each can or bottle.

Alcohol content varies, but one unit is roughly one measure of spirits, half a pint of beer or half a 175ml glass of wine.

Scottish Courage managing director John Dunsmore said: "The introduction of sensible drinking messages on bottles and cans alongside alcohol unit information will help individuals to make better informed decisions about their alcohol consumption."

Drinkaware.co.uk is run by the Portman Group, which is funded by the alcohol industry to promote sensible drinking.

The site, which is currently unavailable but is expected to go live on Saturday, offers an alcohol unit calculator using real drink brands.

A spokesman for the group said it appeared hackers had attacked the site.

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"Some of those who have been able to log on have reported that they have suffered computer viruses.

"We will be very disappointed if we confirm that it has been targeted by hackers."

Unit calculator

It has special sections for drivers, young people, pregnant women, parents and older people.

There is also a simple self-assessment test for people particularly concerned about their drinking habits.

Providing straightforward ways to access advice on problem drinking is a major step forward Dr John Reid Health Secretary

Health Secretary John Reid said: "I welcome the fact that the Portman group of drinks producers accepts its responsibility to give accurate, accessible advice on responsible drinking.

"Companies making it simple to understand exactly the amount of alcohol in their particular drink brands and providing straightforward ways to access advice on problem drinking is a major step forward."

Complex message

Portman Group chief executive Jean Coussins said: "This is a massive step forward towards ensuring that people who choose to drink alcohol can understand fully the responsible drinking message, and can make well-informed choices as a result."

She added that there had always been difficulty "communicating a detailed and complex responsible drinking message... on something as small as a drinks label".