A gay couple living in Wollongong is urging Australians to vote against marriage equality.

Ben Rogers and Mark Poidevin appeared on the nightly current affairs program 7.30 to discuss their views on a non-binding public postal vote on same-sex marriage.

The couple, together 15 years, said that they are committed to preserving marriage as a heterosexual union and would vote against equal marriage for gay and lesbian couples.

Poidevin, a Roman Catholic, said that he worried that extending marriage to gay couples might lead to plural marriages.

“If we make one exception for one community, that being the same-sex couples, where does it stop?” he asked.

“Do we then see other cultures being allowed to have multiple marriages? Do we see the age of consent being lowered for another group of minorities? That is my concern, of where it would lead.”

Rogers pledged that even if the law is changed, he and Poidevin would not be getting hitched.

“We personally will not be getting married,” Rogers said. “We stand by our commitment to each other, we don't need marriage in our lives. Definitely not.”

While voting is not compulsory, a recent survey found that 67 percent of Australians plan to participate in the vote and 63 percent support marriage equality.