Labor says the parliament has the numbers to legalise same-sex marriage and wants Prime Minister Tony Abbott to allow his MPs a free vote on the issue.
Labor's divided factions reached a compromise on marriage equality at the weekend as leader Bill Shorten pledged to act within 100 days should the ALP win the 2016 federal election.
Mr Shorten and senior Labor figures called on Mr Abbott to let Liberal MPs stand up in the parliament for what they believe in.
"We lay down the challenge to Mr Abbott and his Liberals: Please give your members of parliament a free vote so we can make marriage equality a reality now," Mr Shorten told the ALP national conference.
Deputy leader Tanya Plibersek hoped Australia would have marriage equality by Christmas.
"The current parliament has the numbers to pass marriage equality and should be allowed to," she told delegates.
Under Labor's compromise resolution, its federal MPs will be bound to vote for same-sex marriage, but not until after the next two elections.
Mr Shorten's 100-day pledge means that if the ALP wins the 2016 federal election, its MPs will still have a conscience vote rather than a binding one.
The eventual unity on same-sex marriage followed votes on difficult issues including support for the option to turn back asylum seeker boats.
In his final words to delegates, Mr Shorten said the party had established over three days that it was serious about offering a social and economic program for Australia's future.
Labor senator Sam Dastyari said it had been an important conference for Mr Shorten - his first as party leader.
"There is no doubt about it ... Bill Shorten has stamped his authority on the Labor Party."
Liberal Party federal director Brian Loughnane said Labor had no leadership and was divided on key policy.
"Instead of a clear and detailed set of policies for the future of our country, all that eventuated was a series of deals to try and preserve Bill Shorten's shaky leadership," he said.
