But the principal, who read the 'notebook full of pornography' the boy produced in his leisure time, said it was a classic case of how the daily parade of young women in come-hither poses and titillating stories of sex in mass-circulation Chinese newspapers could corrupt the next generation.

'The teacher who found the notebook in the boy's school-bag was horrified,' said the principal of the New Territories school.

'Luckily, it was a male teacher. The women teachers wouldn't go near it.

'The entire notebook is about sex, in lurid detail, written in colloquial Chinese, and complete with drawings.

'I am amazed: there is actually a story line. It is a first-person, fictionalised account of a secondary schoolboy's sexual encounters with a schoolmate and her elder sister.

'There were two drawings showing the boy on top and the facial expressions of the girls. There are descriptions of ejaculation; of how it felt . . . I find it hard to believe he hasn't had sex himself.

'He wouldn't tell us where he got the ideas from. But you can guess,' said the principal.

Exactly who is the culprit, no one can ascertain: Hong Kong's media is full of sleaze. But a quick glance at the popular press may provide an answer.

Last week, Cheng, a Democratic Party member, named five dailies as having questionable standards in its coverage of sex and whose permissive line he finds objectionable.

Apple Daily, which sells an average 295,060 copies a day, devotes almost an entire page to sex everyday.

One column is dedicated to reviewing pornographic videos. One of the two sex series last week likened a woman's breasts to ripening papayas.

A columnist named Fat Dragon gives a daily guide to Portland Street (where a number of brothels are located). Indeed, Fat Dragon is becoming so popular a director plans to feature him in his movies.

Rival newspaper the Oriental Daily News also has its share of such columns - Animal Farm, Forest of Flowers and the Moon.

One of its sexy stories last week featured a menage a trois; another of lesbian sex, and a column praising the French as producers of the world's best pornographic videos.

The Everybody Happy page in Sing Pao carries sex jokes and a column called 100 Love Reports.

Tin Tin Daily News also has its Happy Valley page, where the Sex Traps column last week was a man's account of how he lost his virginity to a lingerie saleswoman.

Hong Kong Daily News, too, finds sex sells - with accounts such as 'I remember my first night', and another saying 'Raped by women ... Why not close your eyes and enjoy it?' But should editors be expected to be moral paragons? Their responsibility is to produce viable newspapers, and some publications see it as their fundamental right to sell themselves with sex.

Ip Yut-kin, the editor-in-chief of Apple Daily, put it simply: 'You cannot omit sex. You have to appeal to the masses and sex helps circulation.' A senior writer with a popular tabloid weekly speaks of a 'pact' between the readers and the people who write salacious articles.

'I don't know who is more guilty. The people who read them or the journalists who write them,' he said.

'We have mothers calling in to complain about our articles and pictures.

'But the mothers read them too. And as long as they keep buying our magazine, our formula of sex and sensationalism will continue. It is the same with newspapers.

'You call it grubby journalism, we call it survival tactics.

The writer elaborated: 'You think we enjoy doing it? We have run cover stories outside of sex and violence to test the market, to find a way out for ourselves. Every time we did, circulation invariably dropped.

'Then we switched back to the old formula, running pictures of scantily-clad stars on our cover and circulation soared.

'Pressure comes from our editors, who are in turn pressed by the owners. On the day the magazine comes out, the editors will be out touring the newsstands. They will find out right away whether this issue sells.

'If it is my cover story, and if it doesn't sell, I will be the butt of jokes during conferences. So what do we do? We need attention-grabbing cover stories, and sex is the easiest subject to write about.

'Who doesn't want to do serious investigative stories? But good ones are difficult to come by. With sex, all you need is to spend several thousand dollars in a nightclub, and the girls will tell you everything.

'Competition is too fierce. There is no time for us to stop to think.

'If during news meetings you say 'hang on a minute, let's be kind', colleagues will give you one of those looks that say: if you want to be kind, why don't you become a social worker?' Ip, a 16-year veteran with Oriental Daily News and its sister publication, Eastweek, before joining Apple Daily, is the champion of the 'anything goes as long as it gets you notice' school of journalism.

His decision to print a picture of the bodies of a woman and her daughter who plunged to their deaths led Apple Daily to issue one of its first apologies to readers.

Recently Ip caused an uproar in the corridors of power when he wrote in his column an analogy suggesting a female legislator might be raped - the legislator had called on a Legco committee to be more cautions in its response to the brutal attack against publisher Leung Tin-wai.

The analogy sparked an outcry. The paper ran the legislator's letter of complaint in full in the same column two days later, but with a cheeky headline: 'Apologise? No Way!' Is this plain arrogance, or a crude attempt to shock? Legco member Cheng, who last week announced results of a survey on lewdness in Chinese newspapers, believes the row between Apple Daily and the female legislator is an isolated incident.

He is more concerned with newspapers' treatment of sex and its influence on youngsters. He is not alone.

According to the poll he conducted, 80 per cent of 623 respondents considered the lewd content of Chinese newspaper supplements a serious problem. More than 60 per cent called for more supervision of newspapers. Almost 40 per cent said there should be more prosecutions. Some respondents suggested that the penalties be raised.

Cheng agrees pornography is not a recent phenomenon but adds: 'This doesn't mean it is right.

'Newspapers are Class I articles under the Control of Obscene and Indecent Articles Ordinance, which means it should not have indecent or obscene content. But I can always find obscene and indecent stuff in some of these newspapers. There is not enough monitoring.' Cheng's call for increased monitoring has led to a heated exchange with the Secretary for Recreation and Culture, Brian Chau Tak-hay, who warned with '50 or 60 patrol teams to check on people selling papers . . . Hong Kong would probably look like a police state'.

Chau says he is strongly committed to freedom of the press and freedom of speech, and the censoring of violence and sex goes against his personal value of freedom.

But is Chau confusing controls on indecent or obscene materials with freedom of speech? Is it not the spirit of the law to protect vulnerable members of the public such as the 13-year-old public schoolboy? Chairman of Chinese University's Department of Psychiatry, Professor Wong Chung-kwong, argues that controlling the accessibility of 'social deviance' such as drugs and pornography would serve to protect vulnerable children.

'Not all children are vulnerable. Pornography is like germs. A healthy child can resist infections; an unhealthy child can't.

'The sex drive is powerful. That is why if a child has an unhealthy upbringing, there could be explosive results when he comes of age.

'This child who draws and writes about sex is perhaps a less worrying case because he could be acting out his fantasy with only pen and paper.

'A worse case is when a teenager, on encountering the opposite sex, thinks of nothing but sex.

'You can argue if a child is healthy, there is no need for a germ-free environment, but that doesn't mean you don't want a clean environment.' Wong Hau-kei, supplements editor of Tin Tin Daily News, said Cheng could have been more objective in his criticisms.

'Our Happy Valley page does not contain indecent or obscene stuff,' said Wong, whose publication was among two of the five newspapers mentioned in this article to respond to our questions. 'If it does, we will be prosecuted. But we have not been prosecuted.' Ip, of Apple Daily, argued that his newspaper had cleaned up its act.

'We have not been prosecuted since February. Before that, we have been prosecuted many times by TELA (Television and Entertainment Licensing Authority).

'Our reporters have been complaining too. So we decided to clean up. The stuff that appears in our supplements now is mild, compared with before.' 'Newspaper operators have [social] responsibilities, but we should also look after the market.

'A newspaper should reflect the society. We have a courts page, a political page - we have a page about night life.' Following the interview, Ip rang back to ask: 'Are you married? Do you make love to your husband?' It is none of his business, of course.

Ip repeated the exchange in his column under the headline 'Why do you have sex with your husband?' His point: the birds and bees is part of life.

But what does a reporter's sex life have to do with the public debate on standards of decency in the media?