Mr Smith also called for an end to the "pathetic political strutting" in Canberra, urging MPs to pass laws to legalise same-sex marriage.

The aviator, conservationist and philanthropist has lambasted all sides of politics for bickering over who or which party should have "ownership" of gay-marriage legislation, and says Prime Minister Tony Abbott should show some leadership on the issue.

The 1986 Australian of the Year says same-sex marriage laws are inevitable and the parliament should just "get down and do it".

"It's a basic human rights issue," Mr Smith said.

"I just turn off with the pathetic political strutting," he said of the developments in Canberra, where momentum for change sparked by a vote in Ireland last month has prompted MPs to come out in growing numbers in support of same-sex marriage laws.

Three bills to legalise gay marriage have already been put forward - by the Greens, Liberal Democrat David Leyonhjelm, and this week by Labor leader Bill Shorten - but none are likely to pass the parliament.

Mr Abbott, faced with momentum for change within his own party, wants a cross-party bill, but which would not be introduced until later in the year.

"We all know it's going to happen," Mr Smith said.

"I wish the prime minister would just do it. Show some leadership and get on with it."

AAP

AAP