Cohabiting has become the norm - 80 per cent of us cohabit before marrying. Since 2001, the number of cohabiting couples in the UK has risen dramatically from 2.1 million to 2.9 million.

The agreed wisdom is that it makes sense to 'test' your relationship by living together and seeing if you can stand the day-to-day reality of each other. An American survey conducted in 2001 found that around two-thirds of twentysomethings believed that moving in together before marriage was a good way to avoid divorce. 

It may therefore come as some surprise that several studies show that couples who live together before marriage are actually more rather than less likely to split up once they do get married.

Furthermore, couples who lived together before they married actually reported being less satisfied afterwards.

So ...what has gone wrong?

Psychologists claim that men and women often start living together for different reasons.

clinical psychologist Dr Helen Nightingale opines 'Women tend to agree to live together because they think it will lead to marriage.'

For men cohabitation is sometimes a way of actually putting off commitment because they're not sure they actually want.

A study in the Journal of Family Psychology found that about 19 per cent of those who cohabited before getting engaged had later suggested divorce compared with just 12 per cent of those who moved in together only after getting engaged and 10 per cent of participants who did not cohabit prior to getting married.

Galena Rhoades, of the University of Denver, explained: 'We think that some couples who move in together without a clear commitment to marriage may wind up sliding into marriage just because they're already cohabiting.'

Clinical psychologist Janice Hiller adds'I see many young couples who've been together for four or five years encounter difficulties. But instead of wondering whether their problems are the signs of something not being right, they get married in the hope that everything will magically get better.'' 

Relationship Counsellor Francine Kay, author of the Divorce Doctor says this about cohabitation:
'You should only agree to it because you want to spend the rest of your life with that person. It should have nothing to do with finances or convenience'

Marriage brings higher expectations, particularly for woemn. What is acceptable from a partner may be simply unacceptable from a spouse.

Divorce lawyer Vanessa Lloyd Platt: 'I hear the same story from clients time after time. Men describe how their partners took a relaxed approach to them going out and doing their own thing while they were cohabiting, but they suddenly started being demanding after the wedding'.

Vanessa adds: 'And from women, I hear that men are irresponsible and want to carry on as if nothing has changed, even after they've got children. Behaviour that is tolerable during cohabitation becomes intolerable when you think you'll be stuck with it for the rest of your life.'

Frances Kay's final advice is this: 'You don't have to get married these days, so it's irresponsible to drift into it. It makes a complete farce of marriage, which is the ultimate expression of commitment.'