Those who seek to win easy votes by legislating to protect children from pornography often fail to envisage the creativity of kids looking to get their hands on any smut at all. When I was in Year 8, if you went to a certain field behind the school and shouted a certain code-word halfway up a certain tree, a pulley would be lowered, at the end of which you would be allowed to glimpse, for a few wicked seconds, a picture of Anna Kournikova's bottom.

I know this because my superior spatial reasoning skills were enlisted in the design of the pulley system, in return for which I didn't get orange juice poured into my rucksack for a whole month. Kids will always find ways to get hold of dirty pictures - and politicians will invariably pitch for votes by trying to stop them.

On 11 October, David Cameron unveiled plans to rescue Britain's children from the swamp of filth seeping out of every node of the web by forcing internet service providers (ISPs) to offer an opt-in system for access to adult content. There isn't much new about these proposals - the main broadband providers already have opt-in services; the only change is that these will now be signalled more effectively.

The official line is that it is all for the sake of the children, but the government is being oddly slow to protect them from more material threats to their health and happiness. Child poverty numbers will rise by 400,000 as a result of present Conservative welfare policies, but the party prefers to embark on symbolic moral crusades that make for tub-thumping tabloid headlines and don't require any real investment. Promising to stop the scary internet from turning our children into depraved little filthwizards is a cheap and easy vote-winner - but the cost of such censorship may be very dear indeed, and not just to those of us who experience our erotic lives bathed in the loving glow of a computer screen.

The Conservatives' faith in filter systems to censor all morally unacceptable websites, and only those websites, approaches the superstitious. There is no magic purity net that can be dragged through cyberspace, and if there was I wouldn't trust Cameron to wield it. Instead, what does and does not constitute adult material will be entirely up to ISPs, angry parents, politicians and private interest groups.

If parents wish to stop their children seeing sphincters do things that sphincters shouldn't, they can easily instal personal filtering software. The imposition of a universal censorship system, however, invariably comes with an agenda.

Unbridled moil

When an Australian government blacklist of adult sites was released by activists, it was found to include many unsmutty sites that someone or other simply didn't want seen, including the website of a tour operator and that of a Queensland dentist. With no oversight, the authorities can, in theory, put any site they like on a banned list.

Pornography is often used as an excuse to enact censorship on a wider scale. This does not mean that pornography is not a problem; nor does it prove that an uncensored internet would be a happy pornotopia of unbridled erotic freedom. Most of the pornography available online, like most of the pornography available offline, is boring, depressing and sexist. With a few exceptions, the pornography production line is managed by a homogeneous, human-hating, profit-hungry industry that chews up the young and vulnerable and disgorges a spiritless procession of carved, shaved, deodorised bodies brutalising one another in pursuit of what the feminist writer Nina Power calls the "grim orgasm of unsmiling physical moil".

The porn industry, with its sterile trade in violent misogyny, is the problem - not pornography. Children will always look for information about sex, and it discredits our culture that sexual hypocrisy has made the porn industry the default place that young people go to learn about what goes where. This is why I am a defender of decent, unbiased, properly funded sex education, and will continue to fight for a world in which we speak honestly to children and adults about sexuality, contraception and sexual violence.

If we want children to grow up in a world in which they can love, learn and experiment without fear of abuse, more education, not more censorship, is the answer.