One in four underage alcohol drinkers consumes more than 20 units a week, a survey claimed today.

Researchers found alarming habits among thousands of young people aged 14 to 17 in north-west England.

One in two young people admitted drinking to get drunk, one in 20 drink alone and one in six regretted having sex after consuming alcohol.

But it also found the number of teenagers drinking alcohol at least once a week has dropped from 50% in 2005 to 38% in 2009.

The survey of 13,000 young people was carried out on behalf of trading standards services in the region and published by the Trading Standards Institute (TSI).

According to Bupa, men should not drink more than 21 units of alcohol a week and women should not drink more than 14 units.

TSI chief executive Ron Gainsford said: "We welcome this broad ranging survey, which provides valuable information for trading standards and other professionals concerned with the safety of our communities.

"It is encouraging that fewer teenagers in the North West are drinking weekly - but the response that a quarter are consuming more than 20 units a week, which is very close to the limit recommended for adult men, is alarming for these young people's own health and for the wider damage on local communities that alcohol abuse inflicts."

Richard Lindley, who worked on the survey, said: "The figures appear to substantiate that the underage sales operations by trading standards at retail premises are working.

"There has been a significant drop since 2007 of young people purchasing alcohol from shops and off-licences.

"It is important, however, that operations aimed at off-licences and newsagents continue, as a priority, to further the decline of the availability of alcohol to young people."

Phil Woolas MP, regional minister for the North West, said: "Although the number of our teenagers regularly drinking alcohol has fallen since the last survey was carried out, the amount that some of them are drinking is worrying.

"The Government's youth action plan set out a range of commitments including stronger powers to tackle unsupervised drinking in public places and also stressed the important role that the alcohol industry has to play in refusing to sell it to under 18s and marketing their products responsibly."

Greater Manchester Police Assistant Chief Constable Garry Shewan said: "Whilst the fall in the number of young people drinking alcohol shows that we are taking the right actions we can not be complacent.

"More and more young people are accessing alcohol from their homes and from older friends.

"We must do more to protect young people and to intervene whenever we see young people misusing alcohol, otherwise they will run a high risk of becoming involved in violence and crime."