Last November, Parliament passed a Greens motion calling on MPs to consult their constituents about who should be entitled to marry. On Tuesday evening the House of Representatives agreed that members should report back in mid-August on those consultations.
Recent polls have shown a slim majority of public support for changing the Marriage Act, but both Prime Minister Julia Gillard and Opposition Leader Tony Abbott have expressed opposition to any amendment.
Last month the Queensland ALP state conference passed a motion calling for changes to the party's national platform in support of same-sex marriage. The Tasmanian, Victorian, Northern Territory and South Australian branches of the Labor Party have passed similar motions.