MARK COLVIN: Three years ago it was hailed as a pioneering case.

Victorian man Liam Magill was awarded $70,000 compensation from his ex-wife after years of paying child support for two children that weren't his.

The court heard that Mr Magill's wife had been having an affair, and when their marriage ended, she demanded child maintenance from Mr Magill even though she suspected he wasn't the biological father.

Today, the Supreme Court of Victoria overturned the judgement.

His supporters, who are calling for law reform, say the ruling is a disgrace and it sends a message to women around the country that it's okay to deceive men.

In Melbourne, Kerri Ritchie reports.

KERRI RITCHIE: Liam Magill was not in court to hear the ruling.

His lawyer Vivien Mavropoulos used just one word to sum up how he would view the decision.

VIVIEN MAVROPOULOS: Harsh.

KERRI RITCHIE: 10 years ago, Liam Magill's world collapsed.

His ex-wife Meredith had told him she suspected he wasn't the father of one of their children.

She'd been having an affair during their four-year marriage.

But DNA tests revealed not one but two of the children were not his.

In 2002, Mr Magill sued his former wife.

The County Court found the law of deceit applied because Mr Magill had been falsely led to believe he was the father of the woman's two younger children. His name was on their birth certificates and on application forms for child support.

He was awarded damages of $70,000 for pain and suffering and past economic losses.

His former wife fought the decision and today, three judges in the Supreme Court in Victoria upheld her appeal.

Vivien Mavropoulos says her client has been "doing it tough" for some time, and today's decision will only add to his distress.

VIVIEN MAVROPOULOS: This will be a big blow for him, that's for sure.

KERRI RITCHIE: The three judges who overturned the ruling handed down a 48-page judgement outlining their reasons.

They found the law of deceit does not apply.

One Judge said he believed Mrs Magill did not "wholly" set out to deceive Mr Magill, and when the children were born she believed her husband was their father.

The court heard it wasn't until much later when Mrs Magill saw her lover's baby photos, that she realised at least one of the children was not Mr Magill's.

The judges agreed this was an unusual case and said their ruling should not be used as a precedent.

Vivien Mavropoulos says her client is considering appealing to the High Court.

VIVIEN MAVROPOULOS: There is definitely a lot of work that needs to be done in the area of paternity deceit.

KERRI RITCHIE: Listening intently in the public gallery today was Warren Lucas.

He says he also discovered he wasn't the biological father of one of his children, and fought to get the money he'd spent over 22 years rearing the child.

The matter was settled out of court.

WARREN LUCAS: The judges are too scared to make a decision because of the implications it's going to cause.

KERRI RITCHIE: Robin Bowles has been a friend of Liam Magill's for four years.

ROBIN BOWLES: You have to understand that this guy found out in a letter, from a DNA lab, that two out of three of his children were not his, many years after they were born, after he'd attended both their births and been their father effectively, all that time.

KERRI RITCHIE: She believes today's decision could have serious consequences.

ROBIN BOWLES: The message it sends to young women is that it's okay to be deceitful and it's okay to cheat in your marriage and then if the child is the result, then hoodwink the husband into paying everything for the children.

KERRI RITCHIE: The Women's Legal Service offered support to Meredith Magill throughout the appeal.

It's spokeswoman, Joanna Fletcher, says it's been an "ugly affair" and Liam Magill should never have pursued the case in court.

JOANNA FLETCHER: Because it's bad for children. You really have to ask how damaging it must be for the children of this marriage to have the man that they've always known as their father, suing their money for an injury and for return of money spent on them, really implying, really saying to them that he got no benefit or joy out of his relationship with them.

KERRI RITCHIE: Meredith Magill didn't want to be interviewed. Her lawyers say she's happy with today's result and now wants to get on with her life.

MARK COLVIN: Kerri Ritchie.