Booming demand for pre-nuptial agreements among wealthy couples

A growing number of lawyers want to give 'pre-nups' legally-binding status, according to the research by accountants Grant Thornton.

At present they are used only as guidance in the divorce court.

Pre-nups have long been popular in America, where they are legally binding.

Couples who have agreed the division of assets if they should separate include Catherine Zeta-Jones and Michael Douglas, Tom Cruise and Katie Holmes and Nicole Kidman and Keith Urban.

The estimated £10million cost of the very public divorce of Sir Paul McCartney and Heather Mills has been a huge incentive to work out the division of assets before marriage, say lawyers.

The former Beatle, who is to pay &£24million to his second wife, turned down a request for a pre-nup on the grounds that it was "unromantic".

The proportion backing the idea to make pre nups legally binding has risen from 37 to 56 per cent, the first time it has gone over 50 per cent.

Robert Kerr, head of Grant Thornton Forensic and Investigations Services, said: "Over the past three years the demand for pre-nuptial agreements has been growing steadily, highlighting that more and more individuals are looking to protect previously acquired wealth upon separation from their spouse."

Although pre-nups can still only be used for the courts' guidance, their legal status has been increasing in recent years.

They were given a boost in December when the Court of Appeal upheld a pre-nup signed by multi-millionaire property developer Stuart Crossley and "serial divorcée" Susan Sangster.

When the marriage failed after 14 months, Mrs Sangster claimed the pre-nup was invalid because her husband had failed to disclose "tens of millions" of pounds in offshore accounts. Her argument was dismissed by the court.

However, the huge increase in " ultra-high net worth" individuals in the UK and the near 50/50 chance that a marriage will end in breakdown, means they are now becoming the norm in Britain.

Mark Harper, family partner at law firm Withers who acted for Mr Crossley, said: "Anyone with significant assets would be mad not to make one."

Karen Jones, editor of the Citywealth newsletter, said there was also a growing trend for "mid-nups" - a review of the pre-nup every five years or so, or if children come along.

"A mid-nup will test validity and keep the pre-nup from being thrown out of court," she added.

Another trend is for parents who have made fortunes to push their children into pre-nups to reduce the chance of a huge chunk of the family's assets being lost to "an outsider".