Support for 'no' vote in same-sex marriage survey grows: Research

Research for Fairfax Media shows support for a 'no' vote is growing while fewer people who back same-sex marriage may cast their vote.

Supporters hand out pamphlets outside the High Court in Melbourne on Thursday, September 7, 2017. Source: AAP

Support for a "no" vote has risen as the same-sex marriage postal survey gets under way.

Turnout among "yes" voters could be very low as well, research for Fairfax Media shows, with a marked drop among those aged 18 to 34.

Years of research has shown most Australians support same-sex marriage and the "no" camp has been seen as the underdog.

But the research shows more people are undecided on how they will vote.