Although the conservative senator does not support gay marriage himself, he suggested all Australians should have a say on any change in law.

"If you are going to make such a fundamental change, it should go to a referendum, I think there is a reasonable argument for that," he told the ABC.

His comment came after Ireland became the first country in the world to approve gay marriage by popular vote.

However Tony Abbott said the question of marriage was "the preserve of the commonwealth parliament" and a referendum was held only to vote on a proposal to change the constitution.

"I don't think anyone's suggesting the Constitution needs to be changed in this respect," he said.

Senator Seselja was not available for further comment later on Sunday.

Australian marriage law is made by the federal parliament and applies throughout the nation, with the states and territories prohibited from making any law inconsistent with the federal Act.

Same-sex marriage was legalised in the ACT in October 2013 but the law was subsequently struck down by the High Court for being constitutionally invalid.

ACT Chief Minister Andrew Barr said the result in Ireland reflected a "remarkable generational shift" in community attitudes.

"It was only two decades ago that Ireland's voters barely approved divorce," he said in a statement.

"The High Court ruling on the ACT's same-sex marriage legislation made it clear that, unlike Ireland, Australia does not require constitutional change to allow marriage equality.

"All that is required is our parliament to reflect the passion for equality and inclusivity of the Australian people. This is routinely reflected in public opinion polls on the subject.

"Australia is stuck in the 1950s on this issue. Our closest international partners have all moved, including conservative administrations in the UK and New Zealand.

"It is time for leadership in the Australian parliament and for community values to be reflected in the law."
Mr Barr, Australia's first openly gay head of government, will split with members of Labor's right faction and vote for a change in the party's national platform, to compel MPs to vote for same-sex marriage.

Federal Labor currently supports same-sex marriage but does not require MPs to support equality in a parliamentary vote.