Senior Abbott government minister Malcolm Turnbull expects parliament to legalise same-sex marriage before the end of the year.
"I have never seen a social issue which has changed attitudes as rapidly as this one," the communications minister told ABC radio on Tuesday, adding his feeling was that legislation was "very likely to pass".
A debate on a Greens bill could start as early as mid-June, but any vote on the issue is likely to fail until coalition MPs are allowed a conscience vote.
Fellow cabinet minister Ian Macfarlane says while same-sex marriage isn't a frontline issue for the government, he's open to having the issue discussed in the Liberal partyroom.
Mr Macfarlane said he continued to oppose legalisation because that was the majority view of the people in his Queensland electorate of Groom.
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"That's my job down here," he told ABC radio from Canberra.
