Something strange is happening to marriage. Even though the statistics go on chronicling its decline – according to the latest figures from the Office of National Statistics, while there were 358,490 marriages in England and Wales in 1950, by 2002 the number had fallen to 254,400 – I have a strong sense that among my contemporaries, people I was at university with in the early 1990s, who were feminists then and still consider themselves to be feminists now, marriage is regaining its popularity. Left-liberal middle-class women and men only ten years older than us might have resisted the idea of marriage; now, it sometimes seems I'm one of the only ones left among my peers who doesn't believe in it. There's another oddity. Marriage may be in overall decline but, if we take an economic indicator, those marriages that do take place are becoming more and more enthusiastically celebrated. According to the National Magazine Company's 'You and Your Wedding' survey, couples spent an average of £15,764 on their wedding last year, and the urban middle-class couples I'm thinking about appear to be leading the trend. Couples are no longer content with a simple service and a marquee in the garden. Modern weddings are conducted in exotic locations in designer bridal gowns, celebrated with fireworks, boat trips and profiterole pyramids. The number of overseas weddings has increased by 55 per cent in the last five years. And it is not enough simply for guests to turn up: they must buy expensive presents, arrange flights and hotels, paint crockery and write poems. Hen and stag nights are also increasingly extravagant. There are now companies dedicated to their organisation, offering activities from hot-air ballooning to health spas, paintballing to makeovers. A study published last year by the market research firm Mintel revealed that more than half of 25–34 year olds have been on a hen or stag weekend, with Dublin, Edinburgh, Prague and Amsterdam the favoured destinations. Once upon a time intended couples might have been embarrassed by such extravagance; now they want the whole meringue.

There's a third puzzling aspect to modern marriage. All this expensive and elaborate celebration goes hand in hand with a persistent cultural denigration of the institution. Marriage, we are constantly told, and not only by Christian groups, has been so devalued and debased that it's not special any more. It has lost its real meaning. Not only is the divorce rate at an all-time high, but marriage is trashed and mocked everywhere you look. In the remake of The Stepford Wives, released this summer, Nicole Kidman's character, a TV executive, is the brains behind I Can Do Better, a reality show in which married couples are tempted into infidelity by glamour models on a desert island. (If this is an attempt at satire, it's blunted by the real life success of an American TV show with the same premise – it's called Temptation Island).

So, how can we handle this contradiction: the evidence that marriage is being given much more significance by some at the very time when it is being most called into question by others? Here's one possible answer. Perhaps the causes of its decline – the secularisation of our society and the wane of the traditional nuclear family – are the very factors that are now prompting the positive evaluation of the institution by the liberal middle classes. It's become a way of holding out against a threatening sense of social fragmentation.

The energy put into making weddings special is an indication of an almost pathological desire to restore meaning to an institution that has lost its function. In the past, the bride's father might have paid for an expensive wedding as a symbolic demonstration to the groom that marrying his daughter was a worthwhile transaction. A wedding was a kind of corporate merger between two families, as well as a ritual enacting the religious and legal sanctioning of sex and childbirth. Now that the original point of marriage has been forgotten, we are investing more and more in making the wedding itself a day to remember.

If you question marriage like this you're likely to be accused of raining on the happy couple's parade. That's because the whole business has become so sincere. We're meant to understand marriage now not as a business transaction but as an expression of love. Some couples claim they're getting married in order to please their parents, others say they want to acknowledge their commitment to each other in public. But really it's all about the fulfilment of romantic ideals, as you can tell from the new-style ceremonies.

Since the reasons are no longer legal or religious, it's becoming more and more common for couples to devise their own ceremonies and write their own vows. The ceremonies tend to contain poems, and sometimes songs. They often make the congregation laugh as well as cry. Generally, they do not mention God, the law, or sex; the emphasis, instead, is on romantic love. Other couples do the opposite: they retreat to the traditional church or synagogue service. Village vicars were in the news recently, complaining that they were inundated with requests from cosmopolitan couples wanting to get married in the church they knew as children, despite the fact that they moved to London years ago and haven't set foot in a church since. Both types of wedding are, in essence, variations on the traditional fairytale ending.

Some, then, choose a humanist ceremony at London Zoo, others dress in charcoal and ivory and make vows before a god they don't believe in. Each is a way of dealing with the confusion surrounding modern marriage, but there are problems with both. Do-it-yourself ceremonies may appear to challenge tradition by updating the wedding for a postmodern world, but they really just paper over the conservatism of marriage while effectively leaving it in place; they fudge the issue. The point of traditional religious rituals was that they had communal force. 'I lose myself in your deep blue eyes' doesn't have the same power, or do the same work, as 'Those whom God has joined together let no man put asunder'.

Couples who adopt religious rituals without being religious themselves are making an even emptier gesture. Non-religious couples who want to marry have an unappealing choice: if they retreat into religious ritual, it won't mean anything to them; if they make up their own ritual, it won't mean anything to anyone else.

All this would be much less troubling, however, if politics weren't at stake. The problem with modern weddings – both lavish and old-fashioned – is that they return us to patriarchal values we thought we'd left behind. Jeanette Winterson argued in the Guardian recently that in mocking the 1950s ideal of the perfect wife, the new Stepford Wives illustrates the great progress made by feminism. But there's a deceit at the heart of this film. For all it pretends to laugh at that 1950s ideal, covertly the film celebrates it.

The gated-community otherworldliness of Stepford bears a striking resemblance to the 'real' world depicted in another recent example of Hollywood neo-conservatism, Sweet Home Alabama. There, similarly, we have Reese Witherspoon playing a powerful female executive, trying to have it all, who gives up her ball-breaking career for a happy marriage. Old-fashioned marriage finds an all-too-comfortable place in these retro, nostalgic times. Sex in the City, Ally McBeal and even Will and Grace sell romantic idealism to female audiences tongue, ostensibly, in cheek. The implication is that as long as we're ironic about it, there's no harm in indulging the archaic iconography of marriage: bridesmaids, tiaras, and a bouquet to be caught by the next woman in line for Mr Right.

Earlier this year in the Guardian, Edith Barton told us why she'd decided to take her husband's name. "I have no defence," she wrote. "To all other extents I'm a modern, independent sort of gal … to take my husband's name seems so old-fashioned, so incredibly unliberated. Women I barely know usher me to one side and explain that taking my husband's name states his ownership of me. But it's not that he owns me, it's simply that I belong to him."

A couple of years ago, the same newspaper ran a column called 'The Wedding Planner', a week-by-week education in the way that lavish wedding expenditure can be a means of recruiting a cosmopolitan, liberal woman for pre-feminism. "I've found my shoes!" Liz Jones exclaimed. "I went into Bottega Veneta on Sloane Street and spotted a brown strappy pair of sandals with a heel encrusted with rhinestones … and the price of £400 seemed very reasonable compared with the £800 pair downstairs." This is fairytale dressed up in irony; backlash in disguise.

Whether it's roses in a pretty country church, razzmatazz in Rio, new age on the beach or new money in Antigua, the modern wedding has become a vehicle for secular people to attempt to revive a lost ideal. If couples are religious, or have the expectation of a traditional marriage embedded in their lives, then fine. But too often, modern marriage results in a dream honeymoon, the unwrapping of gifts – and dodgy political consequences. A previous generation bravely attempted to separate love from marriage; ours is trying – unthinkingly – to force them back together again.