In the United States, polygamous cult leader Warren Jeffs has been sentenced to life imprisonment for crimes including the sexual abuse of a twelve year old "wife". Jeffs, a self-styled prophet who led an offshoot of Mormonism based in West Texas, the Fundamentalist Church of Latter Day Saints, claimed to have 78 wives in all. He also exercised autocratic power in his community and was in the habit of expelling members who declined to hand over their daughters. He treated the case against him in a similarly high-handed manner, dismissing his lawyers and threatening the jury with divine retribution if they convicted him.

Jeffs' crimes are his own, but he fits a recurring pattern in cults and other fringe religious groups, of a guru or prophet helping himself to the sexual favours of numerous female disciples. Mormon founders Joseph Smith and Brigham Young were both keen polygamists at a time when their religion was an object of deep suspicion by most Americans. Indeed, it was only the decision of the Church of Latter Day Saints to renounce polygamy in 1890 that made possible Mormonism's rise to respectability in the United States.

More recently, David Koresh, who perished with many of his followers at Waco, Texas in 1993, is said to have fathered children with several "spiritual wives", some of them under age. Cases like that of Jeffs and Koresh, in which dominant males claim divine sanction for their own sexual gluttony, reinforce the view of polygamy as something both abusive and exotic. And indeed extreme polygamy has traditionally been associated with autocratic and highly patriarchal societies. It would be a mistake, though, to assume that Jeff's version of polygamy represents the usual pattern.

Early Christianity, perhaps influenced by Classical pagan norms, repudiated the polygamy of the Old Testament patriarchs and kings. Monogamy is now the only permissible -- or legally recognised -- form of relationship (certainly the only "normal" one) in much of the world. Yet many cultures have in the past, and some still do, allowed some type of plural marriage. More than 80 per cent of societies listed in the Ethnographic Atlas accepted polygamous unions. Of course, the balance of the sexes means that most marriages, most of the time, will be monogamous. But the concept that monogamy is the only natural or morally allowable type of union is a fairly recent and specifically Western one.

Most notably, Islam permits a man to have up to four wives, although the same opportunity is not extended to women who would like more than one husband. The vast majority of Muslim marriages are of course monogamous, but there undoubtedly are polygamous households in modern Britain. It was recently suggested, in a briefing paper leaked last month to Conservative Home, that all religious marriages be might registered with the state as a way of protecting partners whose arrangements are at present informal. Such a system would inevitably raise the question of what to do about polygamy.

Reports that the government was considering giving recognition to religious polygamous marriages were soon quashed, but the suggestion raises the wider question of the state's involvement in registering and thus endorsing private relationships.

It was straightforward enough when marriage was restricted to heterosexual couples. Recently, however, the privileges and duties (social, but also significantly financial) of marriage have been extended to same-sex couples who chose to enter into civil partnerships. This complicates the picture. By extending recognition to same-sex couples, civil partnerships expand the scope of "marriage" (though the word itself is not used). But they also reinforce the notion of the couple itself as the only valid basis for a relationship, excluding both traditional polygamous unions and more modern, experimental arrangements such as polyamory, in which men and women live together (or separately) in various and shifting combinations. Civil partnerships offer respectability to gay couples but only provided that they are couples -- that is, that they conform to the traditional pattern of Western Christian monogamy.

The civil partnership is the apotheosis of coupledom, the clearest possible demonstration of the official faith (which might almost amount to a religious doctrine) in the moral superiority of the two-person relationship. The marriage/civil partnership system discriminates, more clearly than marriage alone, against those who prefer to live in non-couple relationships -- including polygamous Muslims, polygamous Mormons, polyandrous Tibetan Buddhists (if any such exist in this country) and polyamorous hippies.

There seems little reason in logic for the current legal position. There might be something to be said for insisting on monogamous heterosexual marriage as a way of privileging the country's traditional Christian culture (if that is what you want to do). But once the state recognises homosexual couples it has abandoned any pretence that it is upholding Christian marriage. Whether churches and other religious bodies choose to recognise gay marriage, to the extent of holding ceremonies to honour it, is a matter for them. Unlike heterosexual marriage, they are not able to conduct legally binding partnership in any case. So why stop there? Why not recognise polygamous marriages, and indeed any other form of intimate union that people wish to enter into?

In a liberal society, it is no business of the state's how people conduct their private lives. Some object to polygamy out of the belief that it disadvantages women. But that is not necessarily the case. Some women may actively prefer to be part of a polygamous household, which can have distinct advantages (for example, sharing the burden of childcare) over the standard monogamous unit. As long as there is no coercion involved, the most serious downside may well be in the state's refusal to recognise polygamy and thus give all partners equal rights.

One solution would be for the state to remove itself from marriage registration entirely, freeing people to make their own relationships, religious or secular, monogamous or polygamous -- or whatever else human creativity can devise.