Prime Minister Julia is scheduled to host a dinner date with three gay couples on Tuesday night, in which the small talks are expected to focus on the proposed same-sex union currently lodged at the Parliament.

Gay couple representatives from GetUp! and Australian Marriage Equality are expected to make their case before Ms Gillard, who had earlier declared that she will oppose any bill that will legalise gay marriage in Australia.

According to GetUp! spokesman Sam McLean, the audience with the Prime Minister, which cost $31,000, will serve as a platform for gay rights activists to convince the federal government that "want to get married because they deeply value the institution of marriage."

"In Canberra it is easy to focus on political battles and forget about the people affected by those battles," McLean was reported by the Australian Associated Press (AAP) as saying.

John Dini of Melbourne and his partner, Steve Russell, have been handpicked by GetUp! officials to attend the dinner date that will be held at The Lodge in Canberra.

Dini told ABC that he was happy to lend a face on the campaign for Australia to accept gay union and convey the message that "this is discrimination in so many words and say this is how it impacts on us."

He also believes that the country will finally open its doors for gay marriages, notwithstanding the political force against such union, with both the Labor-led government and the Coalition favouring to reject its legalisation.

"It's taking such a hold worldwide, and obviously Australia will follow suit. So it's really not how, it's a matter of when it's going to happen," Dini said.

Another gay couple, Sharon Dane and Elaine Crump, will also be at hand when the expensive dinner is served.

And like Dini, Dane is confident that the inevitable will happen soon and Australia as a nation will embrace gay unions.

"The whole world is moving in that direction ... and Australia will have to follow suit. It's embarrassing if nothing else," Dane told AAP.

To date, the Australian Parliament is reviewing three private member bills that support same-sex marriage, including one coming from a Labor MP.

While Ms Gillard has explicitly expressed her position on the matter, she allowed the party members to vote basing on their conscience in the event a legislation reaches the voting stage.

On its part, the Coalition maintained its stance of fighting off any attempts to introduce such legislations, with Opposition Leader Tony Abbott reminding Liberals that members risk facing sanctions if they cross party lines.