The US Supreme Court ruling gay marriage legal everywhere in the country "clearly" adds to the momentum for a law change in Australia, Communications Minister Malcolm Turnbull believes.
He agrees with fellow frontbencher Christopher Pyne that same-sex marriage will be on the agenda when parliament resumes after the winter break and a vote should happen before the next election.
"There has been a seachange around the world ... The trend is only going one way," he told ABC TV on Sunday.
Opposition frontbencher Mark Butler said the growing momentum was "irresistible".
"All of the major countries to which we've historically compared ourselves ... all have same sex marriage," Mr Butler told reporters in Adelaide.
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Prime Minister Tony Abbott should "wake up" to the need to allow his colleagues a free vote on marriage equality, he said.
