The two major parties, meanwhile, continued to stress the importance of bipartisanship - while rubbishing the other's standpoint.
Warren Entsch, the Coalition MP spearheading the Government's strategy on same-sex marriage, yesterday again accused Shorten of politicising the issue. The Labor leader countered that Entsch's remarks were "wrong" and "disappointing".
Shorten's bill, which was seconded by his deputy, Tanya Plibersek, would replace the words "man and woman" with "two people" in the Marriage Act.
In his speech, he said that Australian laws "should be a mirror reflecting our great and generous country and our free, inclusive society". To applause from the public gallery, where Shorten's wife, Chloe, was among those present, he added: "Let us delay no more ... Let us make this a reality."
The Government is expected to introduce its own bill, theoretically with multi-party support, in August, when MPs and Senators return from their winter break. The main lobby group, Australian Marriage Equality, has said that - even with a free vote on the Coalition side - it expects the result in the House of Representatives to be close.
Abbott said last week that the landmark social reform - which 72 per cent of Australians support, according to opinion polls - ought to be "owned by the Parliament and not by any particular party". Yesterday he told reporters: "I accept that same-sex marriage is a significant issue. But frankly, this Government's absolute priority ... is to get the most urgent Budget measures through."
In remarks which appeared aimed at dampening expectations, the Prime Minister added: "Obviously there is a community debate taking place. There's a range of views on both sides of the issue and it's an issue upon which decent people can disagree. Let's see where it all goes."