The only way to stop online porn is to force service providers to block it – but we should be careful what we wish for

Dearly beloved: our subject this morning is online pornography and what to do about it. The fact that there is a good deal of erotic material on the net is beyond dispute, though the precise amount is unclear. Let us assume that X % of websites contain porn, where X is a number between 5 and 15. What does that tell us? Answer: an awful lot of people seem to be interested in pornography. If there wasn't a demand, then presumably there wouldn't be such an abundant supply.

In the early days of the web, things were pretty straightforward. As with any novel communications technology, pornographers were early and enthusiastic adopters. In one respect at least they were no different from their predecessors (who likewise exploited photography and movies when those media were new): they had a business model. In the 1990s smut peddlers produced pornographic movies and put them on the web. But they weren't free: punters had to pay by credit card, which effectively meant that hardcore porn was only available to adults.

This kept the problem apparently within manageable bounds. The fact that pornographers found it worth their while to produce and disseminate their wares (which involved some investment and expense) suggested that there was a real market for the stuff. And given that the net effectively lowered what one might call the "shame threshold" (instead of having to sneak furtively into a "specialist" shop, punters could view from the comfort and privacy of their own homes), the internet undoubtedly expanded the market for commercial porn. However much the puritan lobby might dislike this seamier side of human nature, at least the commercial nexus confined it to adults and kept it out of the reach of children.

What upset this apple cart was the rise of user-generated content, aka amateur porn. And this, oddly enough, predated the mainstream net. The culprits were companies like Sony and Panasonic, who brought to market inexpensive, user-friendly camcorders, and software companies who created and marketed affordable video-editing tools. These developments enabled an explosion of amateur porn, usually made by couples who for one reason or another were keen to film their erotic antics. In the beginning, the resulting products were hawked in pubs, but the arrival of broadband connections and hosting services made it inevitable that this (free) user-generated porn would find its way online.

Which brings us to the current outbreak of moral panic (enthusiastically amplified by the Daily Mail) about freely available online pornography. Some of the statistics used to support this panic seem, at best, questionable but that's not to say that there isn't very nasty stuff online – so-called "rape porn" videos, for example. One focus of the current campaign is to close loopholes like the one that makes such videos legal if they are uploaded from locations outside the UK.

That seems reasonable to me. But, in a way, identifying and barring the truly horrible content is the easy part, at least in legal terms. If downloading or viewing certain kinds of online content is deemed illegal, then internet companies know where they stand, and they will obey the law. If a site contains illicit content, then Google et al will find ways of not pointing to it.

The problem is that this alone will not stop people who are willing to take the legal risk implicit in accessing illegitimate sites. The next logical step, therefore, is to make access impossible by forcing internet service providers to block them, using the same technology that the Chinese government employs to make sure that nobody in China learns anything about, say, Falun Gong.

Not surprisingly, nobody in the industry likes this idea. Apart from the extra costs it would impose, it also places companies in the uncomfortable position of deciding what their customers can read and view. And it would effectively put the UK in the same boat as China, Saudi Arabia, Turkmenistan and other countries whose governments decide what citizens can access.

Nevertheless, the ISPs are feeling the heat from a government desperate to be seen to be "doing something" about porn. The biggest four companies (BT, Sky, TalkTalk and Virgin Media) have now "voluntarily" agreed to adopt network-level filtering and will present customers with the option of whether or not to enable it and which "categories" it should block. The only outstanding issues are whether or not any of these categories will come pre-ticked with a "Yes" to enable them; and how many seconds it will take teenagers to change them. This one will run and run.