WH Smith is considering adopting cinema-style classifications, which would give magazines a 15 or 18 age rating according to their sexual or drug-related content.

The newsagent has issued magazine publishers with a consulting document, which proposes introducing the age limits for magazines.

The document also asks publishers for their views on the possiblity of sealing magazines.

The proposal raises fears that magazines like Loaded or FHM might be bagged if WH Smith judges their covers to be too raunchy.

A spokeswoman for WH Smith said: "We are looking at putting together guidelines for all our newspapers and magazines. It's not about censorship."

However, publishers are concerned the classifications could result in men's, clubbing, gay and teen magazines being relegated to unpopular shelves to put them out of the reach of young readers.

One insider, who had seen the document, said "all the sexual content in women's magazines comes under the radar" of the consultation document.

The source added that, under the proposals, the 15 "certificate" would apply to all gay magazines and comics like Viz.

According to the document, WH Smith deems magazines that encourage drug taking or glorify any illegal activitiy as "inappropriate for a family environment".

The retailer also takes issue with magazine covers that bear graphic depictions of "mutilation, deformities or gore" or coverlines that use "language of an insensitive nature".

The lads' mags, FHM, Loaded and Front; clubbing titles, Mixmag and Muzik (which often contain pragmatic advice on drug taking) and raunchy women's magazines like Cosmopolitan and More! could all fall foul of WH Smith's proposed guidelines.

In the discussion paper, WH Smith insists it "will by no means operate as the nation's censor".

Magazine publishers acknowledge that WH Smith - once derided as WH Smug for its conservative attitudes - reviews its policy from time to time and does not want to suppress opinion.

However, one said: "Nonetheless, this sets a worrying precedent of retailers interfering in the content of magazines."