Low prices coupled with high pocket money mean "there has never been a better time" for teenagers to buy lots of cheap drink, a charity has warned.
Alcohol Concern studied how far pocket money could stretch
Alcohol Concern said the price of alcohol had barely risen in 10 years but children's weekly allowances had increased 600% since 1987.
It called for increased taxes on alcohol to deter young drinkers.
But drinks industry body the Portman Group said education was a better way to prevent under-18s abusing alcohol.
Alcohol Concern said it had collected price information from random branches of supermarkets that had previously failed the Home Office's spot-checks for selling alcohol to under-18s.
A teenager could easily buy three times the daily recommended alcohol limit for an adult male, it said.
It focused on brands known to appeal to young people - Bacardi, Bacardi Breezer, WKD, Smirnoff Ice and Budweiser.
With the average weekly allowance for a child aged between 12 and 16 being £9.53, a teenager could spend £7.29 at Co-op on one bottle of Bacardi Superior - containing 13.12 units of alcohol, or 3.28 times a man's recommended daily limit, it said.
Spending £7.98 could get them eight bottles of Smirnoff Ice from Sainsbury's - 9.9 units or 3.3 times a woman's daily limit.
When it came to lager, buying eight bottles of Carling at Sainsbury's could set a teenager back £9 (2.46 times a man's daily limit), with four bottles of Budweiser at Somerfield costing £5.16 (2.2 times).
Alcohol Concern's director of policy and services Don Shenker said: "Young people quite often drink to get drunk.
"When they manage to purchase alcohol, the aim is generally to drink it over the course of one evening.
"Cheap alcohol promotions help explain just why those young people who drink can afford to do so at far greater levels than in the past."
The charity said it was legally impossible under EU competition rules to have a minimum price on public health grounds, but that increased taxation was allowed.
It argued increased taxation could be targeted at products that were particularly appealing to young people.
Mr Shenker added: "Until government gets serious about making alcohol less affordable, it's hard to see how we can prevent young people from cheap alcohol and risky drinking."
David Poley, chief executive of the Portman Group - the drinks industry's social responsibility body - said that better education, not higher prices, was the best method of deterring under-18s from abusing alcohol.
He added: "It seems peculiar to be considering taxing adult drinkers to stop children breaking the law.
"There is a serious problem with underage drinking in the UK, but it is important to acknowledge some positive trends.
"There are now more child abstainers than ever before, and even the numbers of 16-to-24-year-olds binge drinking has been falling since 2003."
Jeremy Beadles, chief executive of the Wine and Spirit Trade Association, said the drinks industry was leading the way with its Challenge 21 initiative.
This encourages anyone who is over 18, but looks under 21, to carry identification.
Mr Beadles said: "It is increasingly difficult for young people to buy alcohol themselves, and the number of under-age drinkers in Britain is falling."