Facebook CEO Mark Zuckerberg changed his status to 'married' recently, but his social-networking website is causing a third of all divorces, a new UK survey has claimed.

According to a the survey, feuding couples are increasingly complaining about their spouse's behaviour on Facebook in divorce filings, with inappropriate messages to the opposite sex being the biggest cause for complaint.

More than 33 per cent of divorces last year listed Facebook as a contributing factor, a study of 5000 divorce petitions by UK law firm Divorce-Online found.

The figure has shot up from just 20 per cent in 2009. "If someone wants to have an affair or flirt with the opposite sex then Facebook is the easiest place to do it," Divorce-Online spokesman Mark Keenan was quoted by the 'DailyMail' as saying.

Incriminating status updates, suspicious check-ins at restaurants and inappropriate photographs being posted online were all increasingly being used as evidence in divorces.

"People need to be careful what they write on their walls as the courts are seeing these posts being used in financial disputes and children cases as evidence," Keenan said.

According to the American Academy of Matrimonial Lawyers, 80 per cent of US divorce attorneys said the number of cases using the social network had increased.

K Jason Krafsky, co-author of 'Facebook and Your Marriage', said office romances and out-of-town affairs that took months or even years to develop in the real world happened "with a lightning speed" on Facebook.

"On Facebook they happen in just a few clicks," he said. Krafsky said the social networking website differed from traditional dating websites in that it both re-connected old flames and allowed people to 'friend' someone they may have only met once or twice.

"It puts temptation in the path of people who would never in a million years risk having an affair," he said.

Even when affairs develop offline, Facebook provides a forum for couples to inadvertently arouse the suspicions of their partners.

The UK study also found couples who had already split up were using Facebook to vent about each other, posting nasty comments for all their friends to see.

Twitter only appeared in 20 of the petitions as part of behaviour allegations. Couples complained their spouses were using twitter to make insensitive comments about them.