Australia's ruling Labour Party agreed to support gay marriage, but consented to lawmakers voting with their conscience on the issue should a same-sex marriage bill come to parliament.
After passionate and emotional speeches from both sides of the debate at the Australian Labour Party conference in Sydney, delegates agreed to change their party platform in favour of marriage equality for gay couples.
The decision, which is at odds with the national ban on same-sex marriage supported by Prime Minister Julia Gillard, was met with rousing applause from the 400 delegates and hailed by supporters as historic.
In opening the debate, Gillard had called for respectful discussion as she acknowledged division within the party on the issue.
"You all know what my views on this debate are and I know many in this hall do not agree with my views," she said.
"But what is the most important thing is that as we have this debate in this hall, we have this debate in a climate and atmosphere of respect."
Gillard, who has said her government will not seek to change the Marriage Act which defines the union as between a man and a woman, had called for the party to accept a conscience vote on the issue.
Her proposal was accepted by a vote of 208 to 184. The vote to change the platform to support gay marriage was accepted on voices.
After the outcome Gillard said the conscience vote, which will likely fail in parliament given that the conservative opposition does not support gay marriage, was "the right decision."
"I wanted to have a conscience vote and we will," she told reporters.
Andrew Barr, the Deputy Chief Minister for the Australian Capital Territory who had called on the national conference to support gay marriage, said a private member's bill on the issue would likely go to parliament in 2012.
"Gay, lesbian, bisexual, transgender and intersex Australians are part of our community," he said.
"We're not nameless, faceless people who live on the margins of society.
"We deserve the respect and the dignity afforded to others. We deserve equality."
His amendment was seconded by Australia's Finance Minister Penny Wong, who said the relationships and aspirations of gays and lesbians were no different from those of their fellow Australians.
"They are also about the sharing of a life together, with all the love, commitment, difficulties, joy and hope this human intimacy brings," she said.
"Our aspirations are not so different. In this, want the same opportunity others have. To make a commitment to another. To have it recognised. To have it respected."
But others within the party, including union leader Joe de Bruyn, argued that changing the platform would cost votes among traditional Labour ranks.
Marriage is mandated by federal legislation in Australia and under the Marriage Act is deemed to be between a man and a woman.
However, same-sex couples have equal rights with heterosexual couples in areas such as pension schemes and medical benefits.
The issue of same-sex marriage was repeatedly raised during the 2010 election and many within Labour have pushed for the party to change its platform.
National convenor of Australian Marriage Equality Alex Greenwich said he was disappointed that the matter would become a conscience vote but hailed the decision as a sign of movement towards marriage equality.
"The momentum for change is unstoppable because marriage equality is an issue which resonates with fundamental Australian values like fairness and inclusion," he said.