Actor Jude Law, former United States President Bill Clinton, footballer Ashley Cole, talkshow host David Letterman and the latest addition: golf superstar Tiger Woods. (Read also: For better or for worse)

What do these famous men have in common?

All of them cheated on their girlfriends or wives.

And the effect of these high-profile cheaters on ordinary guys is alarming, say marriage counsellors and psychiatrists here.

Men are thinking it is okay to cheat too.

“More celebrities cheating desensitises the public to cheating,” says Dr Brian Yeo, a consultant psychiatrist at Mount Elizabeth Medical Centre.

“The fact that many like Letterman continue to hold their jobs, that many like Clinton still have the support of their wives and that many like Woods still maintain their sporting reputations, feeds this desensitisation.”

Another expert, Dr Adrian Wang, a consultant psychiatrist at Gleneagles Medical Centre, agrees.

“There will be a tendency for the average man to think, ‘Even Tiger Woods and Bill Clinton have done it’ and start to validate this behaviour.”

The four experts that Urban spoke to have noticed a jump in the number of couples seeking professional help over their straying partners – up to a 35 per cent increase from 2008 to 2009.

While hardly in Wood’s shameful league – thank goodness – three real-life cheats, who allowed their first names to be used, share their stories.

Their tales come amid rising divorce figures.

A total of 7,220 marital dissolutions were granted in 2008, a 28 per cent spike from 5,651 in 1998, official statistics figures show.

The top three reasons for divorce among non-Muslims in 2008 were separation, unreasonable behaviour and desertion.

The surprising omission was adultery, but Dr Yeo, 48, explains: “Adultery in divorce is always under-reported due to a lack of evidence and avoidance. Many instead opt for clauses such as unreasonable behaviour or separation.”

Veronica Nathan, a senior counsellor at St Andrew’s Lifestreams, a community service arm under St Andrew’s Mission Hospital, expands on this, saying that many straying men file for divorce citing the unreasonable behaviour of their wives, when the real reason is adultery by the men.

“Conversely, going by cases in my practice, eight out of 10 women cite adultery as the main reason for divorce,” says the marriage counsellor of eight years.

Between 1998 and 2008, the proportion of couples divorcing within five to nine years of marriage jumped from 29.6 per cent to 33.6 per cent.

Dr Yeo reckons this reflects the classic seven-year itch, where some couples may feel they are in a rut and look for fresh pastures.

“Couples who can persevere beyond 10 years tend to have worked through their differences,” he notes.

On why some men cheat and others are monogamous marvels, experts point to biological and social reasons.

Dr Lee Cheng, 43, a senior consultant psychiatrist at the Institute of Mental Health, says: “A link between fidelity and a hormone called vasopressin was recently reported. The stronger this hormone is in males, the more likely they are to be faithful to their partners.”

The hormone is found naturally in men and women and regulates levels of water, glucose and salts in the blood by acting on the kidneys. (Read more: Beautiful women more likely to cheat due to hormones)

Dr Yeo, on the other hand, cites a social reason.

“Society accepts men who are more sexually active than women. Men, who are understood to take more dominant positions in relationships, may feel they can easily ignore their spouses and take advantage of other women.”

It does not help that women who are financially dependent on their husbands are also more likely to overlook their infidelities.

“Traditionally, women are more likely to take back their straying spouses due to financial dependence and the need to preserve the family structure,” says Nathan, 49.

Reasons that men have given the marriage experts for cheating include “it developed from a platonic relationship”, “the woman started it”, “looking for excitement”, job stress and loneliness.

Men who have strayed once or twice are more likely to salvage their marriage after the wife finds out, but Nathan notes: “Bad habits die hard. Serial cheaters are very unlikely to salvage their marriage.”

It is not just the men who are wayward, though. Experts say research has shown an increase in older women who cheat. (Read also: It's not just men who are cheating)

“Women are becoming more independent and financially stable. Older, more sexually aggressive ‘cougar’ women are attracting single men,” Dr Yeo says.

Cougars refer to older women on the prowl, a term popularised in the United States, thanks to reality TV shows such as The Cougar.

Dr Yeo, meanwhile, has some advice for Woods, pointing out that the golfer’s hectic travel schedule, financial clout and being “constantly surrounded by groupies” made it easy for him to stray.

The psychiatrist says: “If Woods breaks off from this lifestyle, cuts down on his travelling and spends more time at home, it affords the best chance to stay faithful.”

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