AUSTRALIA'S youngest MP Wyatt Roy has reportedly come out in support of same-sex marriage just days after former Prime Minister Kevin Rudd announced his change of heart.

The 23-year-old LNP Member for Longman has supported marriage equality.

"I support the right of same-sex couples to have their loving and committed relationships recognised in state-sanctioned marriage," Mr Roy is quoted as saying.

Mr Roy's seat, formerly held by Howard government minister Mal Brough, includes the Caboolture Shire, and is generally considered conservative in nature.

Mr Roy said he was aware of the local community's views on the issue.

"I remain vigilant in regard to the views of my local community - and I continue to work through the issues and concerns," he said.

Marriage equality advocates have welcomed Mr Roy's support, saying it reflects generational change in the Liberal Party.

"Wyatt Roy is representative of the strong support for marriage equality among young Australians as well as the next generation of Liberals,'' Australian Marriage Equality national director, Rodney Croome, said in a statement.

"Mr Roy joins the Young Liberals and other future leading Liberals like Kelly O'Dwyer and Simon Birmingham in supporting marriage equality, placing increased pressure on Tony Abbott to allow a conscience vote on the issue."

Mr Croome told APN that Kevin Rudd's statement in support of gay marriage had been a 'game changer' in Australia.

"It has had a huge impact on his fellow MPs,'' he said, adding that it would also influence other Christians to support marriage equality.

"Kevin Rudd is one of the most prominent Australian people of faith,'' Mr Croome said.

He said people were realising that gay people, rather than threatening the institution of marriage, were in support of it.

Australian Marriage Equality has been running a strong campaign targeting MPs who have opposed changes, including Opposition leader Tony Abbott who has refused to support a conscience vote.

Mr Croome said earlier this week that 156,000 letters had been sent by marriage equality supporters through the AME website to Coalition candidates asking them to support a conscience vote.

A national poll conducted last year by Galaxy Research found 73% of Australians support a Coalition conscience vote on marriage equality.