Australia's Ian Thorpe, in front of an Australian flag, holds up the six gold and one silver medal he won at the 17th Commonwealth Games in Manchester in this August 5, 2002 file photo.  [Photo/Agencies]

"The simple fact is that Parliament can change the definition of marriage if it wants to; indeed, Parliament (and other authorities) have been changing it for centuries," he said.

"Widening the definition of marriage beyond the union of a man and woman is also necessary now that the High Court has confirmed some people are neither male nor female but of non-specific sex. These people are currently prevented from entering into marriage with anyone."

The stigma of homosexuality has certainly impacted Thorpe, 31, who has recently battled depression. His struggles reflect Australia's ongoing uncertainty with openly gay national heroes.

"I'm ashamed I didn't come out earlier because I didn't have the courage to do it," Thorpe said in the nationally broadcast interview on Sunday night.

"I didn't know if Australia wanted its champion to be gay," The Olympic champion said.

Former Finance Minister, Labor Senator Penny Wong, Tuesday said Australia is gradually edging closer to same-sex marriage despite several recent attempts falling flat on the floor of parliament.

The well-known gay senator told local radio that the Deputy Opposition Leader Tanya Plibersek also flagged introducing a private member's bill on gay marriage.

Yet Wong still fears what another rebuttal in parliament may do to the same-sex marriage movement.

"We don't want this to fail again -- we want a debate which has the capacity of a bill passing, and marriage equality being achieved," Wong told ABC radio.

Leyonhjelm is hoping his libertarian argument can seduce widespread conservative resistance.

"Of course, while those who have a particular view of marriage should not seek to impose that view on others, neither should it be necessary to approve of other people's marriage choices. Who hasn't met a friend's spouse and thought, 'what does s/he see in him/her?'"

While there is still no federal recognition of gay and lesbian marriage in Australia, the latest social measurement suggests that the Australian public overwhelmingly supports same-sex marriage.

Released this week, a Crosby Textir poll shows that 72 percent of Australians are in favor of legalizing gay marriage, while 77 percent think that Coalition MPs should be given a conscience vote.

Tellingly, Andrew Webster, a leading sports journalist who himself came out on the front page of a leading newspaper late last year, reserved his endorsement of Thorpe's revelations.

"As a gay man, I couldn't be happier for Ian Thorpe. As a journalist, I have misgivings of his outing as a homosexual with legendary interviewer Michael Parkinson, and its timing."

However, while Webster said Thorpe had the opportunity to set the record straight on many occasions, the uncertain response from an adoring Australian public would have been a major impediment.

"That Thorpe is dealing with this now, at the age of 31, illuminates how far Australian society still has to go, and it extends beyond the prime minister's backward thinking about same-sex marriage."