Okay, we have these two digital channels that, to be honest, really aren’t pulling in the viewers. We need something . . . let me think . . . got it! Sex! Brilliant! I’d never have thought of that. And it works, of course. Billie Piper in Secret Diary of a Call Girl pulls in 1.8m for ITV2, and Andrew Davies’s adaptation of Fanny Hill scores 1.1m for BBC4. Result!

Meanwhile, over at Five – remember that? – we have Californication. If you don’t want to explain about nuns and oral sex to the kids, you’d have to be quick with this one. The crazy nun action with David “X-Files” Duchovny starts 2min 13sec after the first credit on the first episode.

Or you could educate them by sitting them in front of The Tudors on good old BBC2. “You see, children, Henry VIII liked to roll around with lots of ladies and Auntie Beeb is going to show you exactly how he did it.”

These four shows have only sex in common. Secret Diary was rotten and The Tudors is risible – Henry may have been a randy psycho but he was also intelligent and cultivated, not something Jonathan Rhys Meyers seems keen to project.

Giving Andrew Davies Fanny Hill – the great dirty book of the 18th century – to adapt is like throwing petrol on the flames. Davies, remember, is the man who sexed up Jane Austen. But he always does it brilliantly and his Fanny Hill is a lot better than the book. Californication, meanwhile, is funny, smart and original as well as being insanely sexed-up.

Leaving issues of quality aside, the not so unique selling proposition of all these shows is sex, lots of it. “I can’t help thinking it’s got a lot to do with the internet,” says Davies, “the ubiquity and accessibility of the most extreme forms of porn have made people used to it.”

Though not actually hardcore, it’s explicit. Tumescent members and penetration may not be on display but almost everything else is. Television was certainly not like this 20 years ago; in fact, it wasn’t even like this five years ago. But now every channel seems to be involved in an arms race of explicitness.

This may backfire. Ratings may soar but revenues may drop. Researchers at Iowa State University found that sexually explicit or violent content makes people forget the advertisements. “One possible reason why sex and violence impair memory for commercials,” said Dr Brad Bushman, “is because people pay attention to sex and violence, thus reducing the amount of attention they pay to commercials.” Gosh, Dr B, you may be on to something there.

Never mind, it’s game on, sexwise. Television wants to give the impression that everybody is at it all the time, that sex is nothing special, it’s just what we really want to do whenever we get the chance.

“One of the things that I like about our show,” Duchovny has remarked about Californication, “is that its approach to sex is kind of something that happens every day. It seems, in movies and TV, sex is this amazing occurrence that is either horrible or transformative. In our show, it is just something that this guy I play falls into sometimes twice a day, sometimes once a week.”

This is an astute summary of what television has done to sex – drained it of emotional significance and turned it into a combination of awkward appetite and power play. Perhaps equally astute was the New York Times critic who described Californication as “male payback for Sex and the City”.

Sex and the City was a sort of femi-nist gesture. It treated men as occasions for sex and women as justifiably predatory. Desperate Housewives picked up the, so to speak, ball and ran with it. The huge success of such shows is, perhaps, the primary inspiration for TV’s current orgy. But does it matter? Do we care?

The answer to the second question is: apparently not. Ofcom, the broadcasting industry regulator, has barely had any complaints about any of these shows – eight for Secret Diary and five for Fanny Hill. For comparison, the series Bringing Up Baby, which subjected babies to a 1950s upbringing, and a Rory Bremner gag about Gordon Brown finding Madeleine McCann for election purposes both inspired hundreds of complaints. Show whatever you like but leave the children out of it seems to be the message.

This confirms Ofcom research that found people were much more offended by bad language than they were by depictions of sex. “The focus groups indicated,” said the report, “that sexual imagery was less of an issue for people than offensive language, particularly in their day-to-day lives.”

So what about the first question: does it matter? Plainly one argument why it does has been lost. Mary White-house campaigned against sex on TV from the early 1960s. She was enormously successful, particularly during the Thatcher years, but mainly as a high-profile symbol rather than an effective check on TV excesses. White-house started from the position that there should be chastity before marriage and fidelity after. Even, it seems, nuns don’t believe this any more.

But without that hardline purity, what is the argument for restraint? Most commonly, it is children. Television operates a 9pm “watershed” – a strange, antique, rural term that now only exists in this context – before which, according to the Ofcom Broadcasting Code, “representations of sexual intercourse must not occur”. And: “Any discussion on, or portrayal of, sexual behaviour must be editorially justified if included before the watershed, or when children are particularly likely to be listening, and must be appropriately limited and inexplicit.”

Is this to save parents from embarrassment or genuinely to protect chil-dren? Research by Rand, the think tank in the US, came to three conclusions about the effect of sex on TV on teenagers: it “hastens the initiation of teen sexual activity”, sexual talk had the same effect as sexual depiction, and discussions of contraception and pregnancy could be usefully educational. More US research by the Kaiser Family Foundation found that the number of sex scenes on TV doubled between 1998 and 2005. So sex on TV alters behaviour and, even leaving aside our current orgy, there is a long-term trend towards ever sexier shows.

Again, does it matter? Teens these days are flung into a world of consumerised sex, of which TV is just one aspect. Parents don’t seem to worry about it; indeed, most seem to encourage the sexualisation of their children. (Perhaps this is why they get so angry about paedophiles – Caliban seeing his face in the mirror.)

We can hardly, in this context, expect TV to hold the line. We can at least agree that preteens should still be protected. But, in that case, the watershed is an idea as antique as its name. “Bedtime” is no longer a potent concept and televisions are in every room as well as online. Maybe we should go for a rating system for TV shows like the one we use in cinemas.

In America, there is an intricate “advisory” system. This became more necessary with the advent of cable networks. Though the main networks – CBS, NBC, ABC, Fox – have stuck, on the whole, to a positively ancient puritan ethic, subscription networks such as HBO and Showtime have been able to go much further. (HBO produced Sex and the City and Showtime backed Californication and, curiously, was one of the distributors of The Tudors. In the latter context, it would be interesting to know who wanted the sexing up, the BBC or Showtime.) At the top of the American ranking is TV-MA, which means the show is for a “mature audience”. Californication is very TV-MA.

These are, of course, purely recommendations. It is difficult to imagine what else might work in the context of the home. Police are hardly going to break down your door on the basis of a tip-off that your 12-year-old is watching Fanny Hill. Furthermore, a ratings system would, almost certainly, result in even more explicit TV as producers felt free to go further with an X rating.

But without any such system and with no credible pressure from either audiences or campaigners to hold them back, how far are the TV people prepared to go? There is, in the present climate, no reason to believe that we shall not have hardcore within a few years. Will it, then, matter? Of course it will. At one level it will be bad for television. Davies points out that hardcore is only watchable alone or with someone with whom you are about to have sex. More explicitness would, therefore, compromise television as a communal medium.

The bigger truth is that the supine viewers and the sexed-up shows are not products, as people so often claim, of sexual liberation or a new openness, nor, indeed, of the expressive requirements of art, they are products of marketing. People have been made to want and accept ever more graphic representations of sex on television. Now they no longer even see it as remotely odd that the only way some dumb producer can communicate that Henry VIII was a bit of a lad is by showing him do the same thing over and over again. Sex on TV makes you go blind.

This matters because, in the end and as we all know, sex is not trivial. If we allow a few marketing jerks to persuade us that it is, then perhaps we shall deserve what we get – a thin, affectless world of appetite and power. Is that what you really want, Mr TV Producer? It’s your call.

Editor's choice

• U2 at Nou Camp Stadium, Barcelona
• The 50 Best Movie Villains
• The 15 golden rules of theatre etiquette