Opposition Leader Tony Abbott has given his strongest indication he won't support a conscience vote for Liberal MPs on gay reform, reminding his colleagues that each of them were elected on a platform of opposing same-sex marriage.

"It was the clear policy of the coalition at the election that marriage was between a man and a woman," Mr Abbott told Sky News today.

"Every single member of the coalition was elected on that position and I don't think we can break faith with the electorate."

Mr Abbott said although shadow cabinet would not finalise its decision until after the issue went before the party room early in 2012, he did not see any reason for the coalition party to change its stance.

"I don't see any fundamental differences in objective reality today that would justify any change of a fundamental commitment like that," he said.

"I know that in their heart of hearts there would be a few of my members who would prefer it to be otherwise, but that was the commitment that every single one of us took to the election."

Earlier this month, the ALP National Conference voted to support same-sex marriage.

Prime Minister Julia Gillard agreed that Labor MPs could vote on a bill on same-sex marriage according to their consciences. A bill is expected to come before parliament next year.

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