The Scottish government will this week launch its biggest assault on binge drinking, banning the sale of cheap alcohol by supermarkets and off-licences and raising the buying age to 21.

New legislation will seek to impose a minimum price at which alcohol can be sold — expected to be around 40p per unit — and there will be a ban on cheap drinks promotions such as buy one get one free offers.

The measures will end the supermarket practice of selling alcohol in large volumes at rock bottom prices, which has been condemned by public health experts for encouraging shoppers to buy more than they want and fuelling excessive drinking.

In addition it will be illegal for anyone under the age of 21 to buy alcohol to take away, although people will continue to be served in pubs at 18.

The measures, to be announced by justice secretary Kenny MacAskill on Tuesday, are aimed at arresting a recent rise in binge drinking and alcohol-related violence. Scotland has Europe’s highest levels of drink-related illnesses at a cost to the health service of more than £1 billion a year.

The availability of large quantities of cheap, freely available alcohol has been blamed for exacerbating the problem. Imposing a minimum price of 40p per unit of alcohol would raise the cost of the cheapest drinks, such as super-strength beers and cider, by up to 400%.

“We simply cannot go on allowing shops to sell superstrength beer and lager for less than the price of water,” said a source close to the Scottish government.

“Pubs have taken great strides to clean up their act and control how people drink there, but there are still problems with underage kids getting hold of cheap, strong booze over the counter and getting tanked up and causing problems for themselves and others.”

The progress of the policy, which must be passed by the Holyrood parliament, will be watched closely in Westminster. The UK government introduced bans on smoking in enclosed public places and raised the tobacco buying age to 18 after observing these measures in Scotland.

Chancellor Alistair Darling raised levies on alcohol in March amid fears that low supermarket prices are fuelling binge drinking, violence and health problems. Pat McFadden, the business minister, has now confirmed that the UK government is also considering introducing a minimum price for alcohol in England and Wales.

Supermarket own-brand cider is sold for as little as 11p per unit and Stella Artois lager for 30p per unit. Imposing a 40p minimum price per unit of alcohol would increase the cost of a two-litre bottle of Tesco own-brand dry cider from 94p to £3.36 and 12 500ml cans of own-brand lager from £6.84 to £9.60.

It will bring the law in Scotland into line with America, where selling drink to under 21s has been banned for more than 20 years. Supporters of the US law say it has made under-age drinking more difficult, and it is credited with saving lives by reducing drink-driving. A study by the US National Highway Traffic Safety Administration claimed the higher age limit had cut fatalities by 13% among 18 to 20-year-olds.

Sweden and Iceland refuse to sell alcohol over the counter to anyone under 20, while in France, Italy, Spain and Portugal the age limit for buying alcohol over the counter is 16.

Jack Law, chief executive of Alcohol Focus Scotland, said: “As part of an overall package there is every reason to raise the age for buying alcohol at off-sales where drink can be three times less expensive.”

The Wine and Spirit Trade Association described the new measures as “ridiculous”.

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