We Brits do like to titter about sex, a legacy of Benny Hill, Sid James et al. The kinky suburban couple is an archetype; what alternative uses they find for feather dusters is the source of puerile but innocent humour. Such high jinks aren't doing anyone any harm - or so many of us are inclined to think.

That benign view might have sufficed once, but not any more, not according to the Scottish Government. Why? The internet. This week, Justice Minister Kenny MacAskill has lifted the lid on the violent side of internet porn, a world easily accessed from home, where images of rape and violence against women are rife. He has warned that those who download images of rape and other extreme pornography are encouraging the abuse and degradation of women. So he is to bring forward proposals making it a criminal offence. Those who are found in possession of downloaded images could face up to three years in prison.

At present, it is illegal under Scots law to import or supply extreme porn, or possess it with intention to sell. In England and Wales, the Criminal Justice and Immigration Act 2008 also made owning such pictures an offence. Mr MacAskill now wants to go further than the English legislation, not only banning possession of extreme porn which results or appears likely to result in serious injury, but outlawing any image of rape.

Defenders of personal freedom are fearful that this constitutes a move by government to censor the behaviour of consenting adults, and they are right to demand a debate. It is not up to the government to outlaw people's sexual fantasies. This is a complex matter: by criminalising adults who view images of other consenting adults, the government risks an erosion of civil liberties.

But at the heart of the matter is the question of criminality. In the lawless alleyways of cyberspace, where images can be uploaded from anywhere in the world, it's impossible to know whether certain depictions of rape are real or reconstructed, and to what extent the women involved have been coerced - almost as impossible as it is to police it. As we know already from the fight against child pornography, preventing illegal acts being filmed and uploaded in the first place is as difficult a task as any facing law enforcers. Targeting those who pay to view such images, though, is one area where national governments usefully can take action.

To be clear, we are not talking about merely explicit images. We are talking about feeding an appetite for imagery depicting women's humiliation and pain. Taglines such as "these girls say no but we say yes" leave no doubt as to the selling point. Some sites feature re-enactments; others bill themselves as real rapes.

It's crucial that the law strikes a balance. The libertarian view is that the government is becoming a sort of prurient Peeping Tom, inviting itself into people's bedrooms where it has no place to be. You may not like the idea of the "rape fantasy", they argue, you may find it distasteful, but it's none of your business what consenting adults want to view in the privacy of their own homes. If it is to be effective, the legislation must be carefully considered on a case by case basis. The indications are, for instance, that those who accidentally access extreme porn by clicking on the wrong button will not be at risk: that makes sense.

A debate is certain, not least because the issue of sexual violence in Scotland, and how we deal with it, is such a cause for concern. The conviction rate for reported rapes in 2006-07 was 2.9%. Research conducted by Rape Crisis last year found 27% of Scots believed women who dressed in revealing clothing could be at least partly responsible for being raped. A further 24% thought a woman was in some way responsible if she was drunk and 29% if she was flirting. These are medieval attitudes.

We should not shy away from considering the wider effects of rape fantasy material online. The positive spin is that it's the preserve of the sexually liberated men and women in respectful, trusting relationships who flit seamlessly between bedroom role-playing and companionably sharing the housework. Yet does anyone really believe it begins and ends there? We ignore the rape fantasy phenomenon at our peril. Such images are prolific and easier to access than they have ever been. How is it affecting men's attitudes to sex? Are people who view such material already turned on by the idea of violence towards women? Do they become so, or more so, after watching it? Does it change men's attitudes about the gravity of rape as a crime? At least one Canadian study suggests it does, but more research should be done.

These are crucial questions and we need a definitive view on them. Only then can we judge the extent to which these sites encourage rape as well as depict it. This is the beginning of a process and it must have the protection of women at its heart.

Click here to comment on this story...