So, where have all the men gone?

Britain is becoming a nation of home-alone women. According to the Office for National Statistics, there is a growing imbalance between the sexes, and a marked tendency for people to live alone. The next two decades will see a 10 per cent rise in the number of bachelors but a 12.3 per cent increase in single women, while the number of people living solitary lives has risen from 370,000 in the Seventies to around 1 million today.

The lack of a partner is particularly besetting independent, successful career women in their late twenties, thirties and forties, just as it has done in America for several years. The plaintive cry "Where have all the eligible men gone?" is now heard as much in London as it is in Manhattan.

The dearth of suitable males is the subject of Julia Roberts's new hit movie and in New York the seriousness of the situation for women of a certain age who want to have children has led to a series of magazine articles on the subject. One of the latest, in the monthly Harper's Bazaar, is a poignant confession by writer Christa Worthington that she is thinking of becoming an SMC - a single mother by choice, through artificial insemination.

Now a Channel Four documentary on the subject is in production here in Britain, exploring the phenomenon of single women which has led to an explosion in the number of dating agencies. Around 100 of them are flourishing, serving up to 10,000 people each.

The growth of the single life has come about through profound social change. People are marrying later - in 1983 the average age for getting wed was 26 for men and 24 for women - and in 1993 it was 29 for men and 27 for women. Men who marry late often pick a younger woman rather than someone their own age, leaving a whole raft of women over the age of 30 without a suitable partner. The growing confidence with which men can come out is also blamed for a shortage of eligible men; in London, according to gay pressure group Stonewall, up to 15 per cent of men are homosexual.

Those who are interested in women, say dating agencies, don't always like women who are successful. They believe that a lonely heart advert for a man that says he is successful attracts plenty of response. For a woman to describe herself thus is often a turn-off.

In New York, says publisher Sarah Giles, success is not so much a problem. "Men here like powerful women. It's a turn-on. But back in Britain I know it's not the case." Being single, though, can be a stigma in the social hothouse of Manhattan. Miss Giles recalls that the New York gossip columnist Liz Smith reacted in horror when she told her that she was on her own after a relationship ended. "She said to me: 'There's nothing worse than being a single woman in New York.' "

According to Miss Giles, one of the most popular ways for affluent, New York career women to find men is to use blind dates, organised by friends. In Britain, those whose lives have been given up to the pressures of work often bypass traditional courtship for the colder, more businesslike world of dating agencies. Lonely heart ads, once viewed as the province of the sad and rejected, have never been more popular or more acceptable.

Mavis Cheek, who wrote her novel Aunt Margaret's Lover, about a quest for love through such ads, after meeting a series of men this way to research her book, believes that women of 40 and 50 are quite different from those of a previous generation.

"There was a time when a woman who was left on her own by the time she was in her forties or fifties would just accept that she would be alone for the rest of her life. She just waited to get old. Now, women are not prepared to do that. They are still out there, looking for someone, and are still attractive, sexy women."

For a generation brought up to believe that they were part of the "have it all" era, the discovery that putting career first and a long-term relationship second has its price can be a shock.

"I always had boyfriends, lots of fun, but the thing I was most committed to was my career," says charity worker Sue Lockwood. "As I got to 30, the thought hit me that I was never going to be anything other than single. There is something pointless about it, a life without validity."

In her latest film, My Best Friend's Wedding, Julia Roberts plays a character who frets at being 28 and unmarried. The film, which has broken box office records, ends with Roberts winning as her consolation prize Rupert Everett, a gay friend who warns her that she may never get married and must make the best of it.

Not all career women see the single life as a bad choice. Instead, they have become increasingly choosy - or cautious, as 50-year-old Ms Cheek, puts it - about who they see. Alison Stephens, a 39-year-old businesswoman who runs her own import/export firm, has lived alone for 12 years.

"Being single is a choice, and I would be loathe to give up my territory. Part of that territory is my business and is very precious, and is what really motivates me. The difficulty with men is that you can make them uneasy if you are successful. When I earned more than my boyfriend he became jealous, as if his manhood was under threat."

For many single women, the alternative to the security and support from a partner is the networks they have created between themselves. Jeffrey Weeks, author of a South Bank University report on what he terms these "families of choice", says that "for many people today, family means something more than biological affinity or the unit created by marriage. It means something you create for yourself, something that involves interactions, commitment and obligations that have to be negotiated."

For women without partners or children, old age is a prospect often dreaded. The actress Julie Christie, never married, is planning her own family of choice when she is a pensioner and spoke last week of her intention to move abroad with friends like her. "We've got to live close," she explained, "and though we'll be dying off, we can be a rather elderly family to each other."