Australia is seen as lagging behind a growing number of countries on marriage reform and popular support for change is high
Thousands of people rallied in Australian cities over the weekend in support of same-sex marriage, as politicians across multiple parties prepared to submit a bill to make the unions a legal right.
More than 4,000 gathered in central Sydney in a colourful march, chanting "Put the bill, pass the bill, marriage rights now!" and carrying banners reading "Love is love".
"We're going to come back to the streets again and again until we win," march organiser Rachel Evans from activist group Community Action Against Homophobia told the cheering crowd.
Similar rallies were held in Perth on Sunday and in Brisbane and Hobart on Saturday. Supporters of marriage equality will hold rallies in Melbourne and Adelaide next weekend.
"This is the height of the campaign," Evans told AFP in Sydney. "It's one of the largest rallies."
One of those taking part, Matthew Higgs, said he was raised by his mother and her partner and wanted equal rights for them.
"She's been with her partner for a long time," he told AFP.
Sally Rugg, with activist group GetUp, told the crowd that support for the issue went beyond marriage rights and sent a message to the community that gay people were accepted.
A backbencher from the ruling Liberal Party -- seconded by an opposition Labor representative and with co-sponsors from other parties -- was set to introduce a marriage equality bill as parliament resumes this week.
Prime Minister Tony Abbott, a staunch Catholic who opposes changes to the Marriage Act, last month played down prospects of the private member's bill being debated and voted on in parliament.
His conservative government is opposed to gay marriage and the party has previously refused to allow a conscience vote among its members, in contrast to the Labor opposition.
A vote on the issue in 2012 was defeated 98-42 after Abbott -- whose sister Christine is gay -- did not allow his MPs, then in opposition, to break party lines.
But there has been increasing support for same-sex marriage, with a poll last year finding those in favour of equal rights had reached a record high of 72 percent.
There has also been growing pressure on the issue following the US Supreme Court's recent ruling legalising same-sex marriage nationwide, and Ireland's referendum in favour of gay marriage.
Local celebrities including Hollywood actor Hugo Weaving are set to star in a series of "We Can Do This" television advertisements airing from Sunday and supported by gay rights group Australian Marriage Equality.