SEX and glamour have transformed the teen mag from being a tribute title to David Cassidy to a multi-million-pound business.

The posers: “Am I too young to have sex?” and “What happens at a rave?” are the staple diet of the new breed of magazine.

Before the mid-1980s, teenage girls were served up comic strips and encouraged to wear tartan.

Everybody’s favourite, Jackie, which dominated the early scene, touched on the subject of snogs behind the bike shed but was just as likely to feature a photo story about a girl and her pet pooch - “Love me, love my dog”.

Just 17 (now J17), launched 15 years ago, marked a revolution in teen mags that has seen them develop into mini-Marie Claires and an industry worth pound;70 million.

Marie O’Riordan, group publishing director of youth magazines at Emap Elan, said: “Up until that point, girls went from reading Jackie and Bunty, which were basically comics, to lifestyle titles like Cosmo and Marie Claire. Just 17 was the first magazine for teenagers who wanted something a bit more sexy and glamorous.”

As a result of J17‘s success, teen titles have proliferated - Big! and Smash Hits (aimed at 12-year-olds) Mizz (13-year-olds), MG, Bliss and 19 (17-plus).

Fashion, emotional issues, horoscopes, celebrity gossip and beauty tips fill the high-gloss pages. And, of course, there are the pieces on sex which cause regular outrage with subject matter increasingly close to the knuckle. In 1995 TV Hits, aimed at 10 to 19-year-olds, caused an uproar when it published explicit advice on oral sex in response to a reader’s letter.

Like women’s magazines, each has its own style. MG (My Guy) favours the photo-strip and even has its own soap, Kingsbrook. But it is considered down-market compared to Sugar - which has campaigning articles against the fur trade and harder-edged stories suchas “My mum was murdered in front of my eyes”.

Bliss claims to be “The Smart Girls Guide To Life” and offers 23 different “love” quizzes this month. Four counsellors answer youngsters’ questions on love, life, sex and body worries. The magazine has warned its readers that it has no more work experience places until November 2000.

Research by Emap Elan shows that in the UK 72 per cent of girls read magazines, compared to 58 per cent of adult women.

Ms O’Riordan said: “I think the market really peaked in 1998 when the Spice Girls focused the world on girl power and teenage culture in general, but the interesting thing is that there is much more loyalty among teenage girls than adults.

“Whereas a woman will go for the magazine that has a cover line that interests her, or a free gift that appeals, girls are far less fickle. They find the magazine that appeals to them and stick to it for years.”

Teen mags have proved so profitable that publishers have been able to create niche markets. The re-launched Just 17, J17, is aimed at ABC1 teenagers. It has a circulation figure of 328,382 and is well above other teen titles.

Boys get less choice in comparison. For the football fanatics there are publications like Shoot and Super Reds, the unofficial fan mag for Manchester United.

There are also computer game magazines such as Arcade and Nintendo but no real “lifestyle” magazine. An experimental title, FRONT, was launched 18 months ago as a junior version of Loaded and FHM but publishers found teenage boys were already buying the hard-core versions.

Magazines such as FHX and Disney’s Big Time are closely tied to TV. In these, as in some of the football magazines, the Japanese “pocket monster” Pokemon features heavily - Pokemon guides, stickers and pull-outs are big now. Top of the Pops and Smash Hits appeal to both genders and still provide the posters that adorn many a teenage bedroom.