The survey of 100 leading divorce lawyers in England and Wales pointed out that growing numbers of people are divorcing because of "mid-life crisis".

Extramarital affairs were the most common cause of marriage breakdown for the survey's fifth year running, accounting for 29 per cent of divorces in 2007, down from 32 per cent the previous year. But mid-life crisis took second place for the first time, rising from 2 per cent in 2006 to 14 per cent last year. Family strains were the third most common cause, at 11 per cent.

The report, from chartered accountants Grant Thornton, published in The Guardian on Monday, found that two out of three lawyers surveyed had at least one client in 2007 who hired detectives to shadow a spouse suspected of cheating.

Tamara Mellon, founder of the Jimmy Choo shoe empire, was spied on by private investigators hired by her husband, Matthew, during an acrimonious divorce last year. But in 64 per cent of cases the suspicious spouse was the wife.

"While it might seem like an extreme length to go to, people just want to know the truth - even if it hurts," said Andrea McLaren, head of Grant Thornton's London matrimonial practice.

According to the survey, 78 per cent of the straying spouse is usually the husband. The percentage of cases in which the wife is the guilty party dropped from 31 per cent in 2006 to only 22 per cent in 2007.

The British survey by chartered accountants Grant Thornton showed that in the majority of mid-life crisis cases - 93 per cent - the partner having the crisis was the man.

Sir Mark Potter, president of high court's family division, acknowledged that London has become "the divorce capital of the world."

About 94 per cent of the family lawyers polled by Grant Thornton named England and Wales as the best place for a wife to have her divorce dealt with.