Tony Abbott has all but ruled out holding a referendum on same-sex marriage, saying the federal parliament will deal with the matter if it's brought to a vote again.

Asked today whether Australia will follow Ireland in holding a popular vote on gay marriage - Mr Abbott says referendums in this country are reserved for approving constitutional changes.

Mr Abbott today recommitted to letting the coalition party room decide whether MPs would get a free vote on the matter, should any legislation get to that point in parliament.

The announcement comes after Federal MPs of all stripes have argued Australia should follow Ireland and have a referendum on gay marriage.

Ireland has become the first country in the world to approve gay marriage by popular vote, with 62 per cent voting 'Yes'.

Liberal Senator Zed Seselja says fundamental change like gay marriage reform should go to a referendum, though he does not support it himself.

Independent Jacqui Lambie backs a referendum over a conscience vote of the federal parliament, but like Senator Seselja does not support gay marriage.

Meanwhile, Independent senator Nick Xenophon says he would support a referendum if that was a "circuit breaker" in the long-running debate.

Gay activists are convinced the usually conservative country's strong approval of same-sex marriage will have repercussions in Australia.

Australian Marriage Equality director Rodney Croome says Australians will be "scratching their heads" over why the federal parliament does not support reform.

But a group against same-sex marriage has vowed not to let Australia go the same way as Ireland.

The result has spurred a strong response from the Australian Marriage Forum, who call it a "day of shame" for Ireland.