For Tanya Plibersek, the deputy leader of Australia's Labor Party, legalising same-sex marriage is a simple matter of righting an injustice.

"I think this is an issue of legal discrimination against one group in our community," she said on ABC's Q&A program Monday night. "Do we have a conscience vote about whether we allow racism in our community? Do we have a conscience vote on whether we allow sexism or ageism? We don't."

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While Labor's platform has supported same-sex marriage since 2011, its members are currently permitted a conscience vote when a marriage equality bill comes before parliament. A conscience vote — a rare occurrence in Australia — allows members of parliament (MPs) to vote as their own moral, religious or political beliefs dictate on topics such as abortion and euthanasia, and not along party lines.

Plibersek wants to change that. At the party's national conference in July, she intends to push for Labor MPs to be bound to vote for same-sex marriage, she told Fairfax Media.

"Conscience votes in the Labor Party are reserved for issues of life or death," she said during Q&A. As same-sex marriage doesn't fall into that category, according to Plibersek, a conscience vote is unnecessary and stands in the way of freedom from discrimination for homosexual people in Australia.

Prime Minister Tony Abbott, who is the leader of the Liberal Party and a same-sex marriage opponent, announced before the 2013 election his party room would debate allowing Liberal MPs a conscience vote on gay marriage, but the matter is yet to be raised.

Australian Marriage Equality National Director Rodney Croome said in a statement he welcomed Plibersek's position. "If successful, it will help break the current deadlock over marriage equality," he said. "A Labor binding vote and a [Liberal] free vote would be a recalibration to the normal situation and allow Australia to finally achieve marriage equality."

Croome told Mashable Australia a binding vote for Labor would increase the likelihood of marriage equality being passed. "In the current parliament, I think there would be enough support in the Liberal Party to make the passage of marriage equality quite likely," he said.

In the wake of Plibersek's announcement, however, some believe the prospect of a Liberal conscience vote is dead.

Dean Smith, the Liberal Party's first openly gay senator and a supporter of same-sex marriage, told Fairfax Media if Labor adopted a binding vote on gay marriage, the Liberal Party would not go forward with a conscience vote. "Conservatives who oppose same-sex marriage and a conscience vote will be sitting pretty," he said. "There has been a slow and cautious approach to achieving a conscience vote and she has wrecked that."

For some same-sex marriage supporters, however, the question is already a tad passé.