Sweden, one of the world's most sexually tolerant societies, is in the throes of a strange, emotionally charged debate about the last taboo: bestiality.

The unmasking this week of an animal sex network by the Stockholm newspaper Expressen has again highlighted the issue. Members of parliament are urging a tightening of the laws (bestiality was decriminalised along with homosexuality in 1944) but the government is resisting the pressure.

“Should a human be allowed to affectionately stroke the teats of a female dog?" asked Eskil Erlandsson, the Agriculture minister, explaining the complexities of an anti-bestiality law, "or does that count as the sexual abuse of an animal?" The minister, famed for his outspoken manner, later left many Swedes aghast when he gave an even more explicit example.

The Minister's concern was stirred by figures and projections from animal welfare groups. One, the Swedish Animal Welfare Agency, registered 115 cases of bestiality between 2000 and 2005. This is regarded however as the tip of the iceberg and some published projections suggest that between 200 and 300 dogs and cats a year are being sexually assaulted.

The Expressen story has stoked up the debate even more. It infiltrated a reporters into a group run by the organiser of a flourishing internet animal sex forum. He owns a farm with dogs and horses and told the newspaper that he had regular sex with his female dog but claimed the animal initiated the act. This is a sufficient defence under current Swedish laws to prevent prosecution under charges of animal cruelty.

The network of around 30 people, mainly men, organise regular rendezvous with different farmyard animals and dogs. The events are often filmed for later use in pornographic films.

Sweden has had a pioneering approach towards sex, at least since the 1960s when critically acclaimed films such as I am Curious Yellow depicted the society's free-wheeling attitudes. The country was one of the first to shed the stigma of single motherhood and, while Swedes talk less about sexual matters nowadays than 30 years ago, they are still pushing back the boundaries. Pharmacies, for example, have just been authorised to sell female sex toys across the counter. Legal limits are set mainly on the commercial exploitation of sex: thus, while prostitution is technically legal, customers are seen as offenders who exploit and abuse women. Cameras have been set up near the entrances of brothels and clients leaving the premises can be fined on the spot.

But bestiality and the whole seedy sub-culture surrounding it is straining Swedish tolerance to bursting point. Religious Swedes say it violates a fundamental taboo: a passage from Leviticus 18 states: “And you shall not lie with any beast and defile yourself with it, neither shall any woman give herself a beast to lie with it: it is a perversion." In the Middle Ages, men were typically burned to death for having sex with animals. Most countries nowadays either outlaw the practice entirely (most states in the US) or prosecute penetrative sex with animals (Britain). Sweden, though, has not taken a religion-based stance. Rather, it seems to accept the idea that sex with animals can be in some way consensual. If it causes injury to the animal it can be prosecuted, although in practice only two out of the 115 cases registered have ever been investigated.

Jan Ertsborn, a Liberal member of parliament, told the Swedish-based news website thelocal.se: “Veterinarians see a lot of injuries that they believe are caused by this behaviour but it is difficult to prove." Mr Ertsborn is leading the campaign to impose a legal ban on bestiality. A national petition has been launched in support of his initiative and it is supported above all by equestrians anxious about the number of cases of people who clamber over farm fences at night and attempt to rape female horses. A similar wave of horse abuse has been noted in Germany.

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