Third Nationals MP backs same-sex marriage

A third federal Nationals MP has publicly declared his support for same-sex marriage.

After colleagues Darren Chester and Indigenous Affairs Minister Nigel Scullion revealed they were in favour, Kevin Hogan has joined them, but on the condition churches aren't forced to marry same-sex couples.

"If those protections are there though and I'm comfortable that those protections are there (I will support it)," Mr Hogan told ABC radio on Thursday, adding he would prefer the people to have a say in a plebiscite.

Parliamentary Secretary Concetta Fierravanti-Wells urged against a conscience vote for Liberal MPs, describing it as proxy for support of same-sex marriage.

"This is not a change the parliamentary Liberal party can make without extensive consultation with those thousands of party members for whom marriage is a fundamental bedrock belief," she told the Australian Financial Review on Thursday.

Senator Fierravanti-Wells, whose responsibilities include multicultural affairs, also warned there is strong opposition to same-sex marriage within ethnic communities.