SYDNEY (AFP) - Australia's ruling and opposition parties vowed on Friday (Sept 8) to work together to introduce laws against hate speech ahead of a contentious postal vote on gay marriage.

Same-sex marriage advocates have opposed the voluntary postal ballot that opens next week, arguing it could turn ugly and expose gay people and their families to abuse.

Despite growing public support for same-sex marriage, Australia has not yet legalised such unions after more than a decade of political wrangling.

Prime Minister Malcolm Turnbull last year pledged to hold a national referendum, but switched to a postal vote when the original plan was twice rejected by the upper house.

Some 15 million Australians will receive ballot papers after the High Court on Thursday threw out two challenges against the survey by marriage equality campaigners.

The hate speech fears have led to the ruling conservative coalition and the left-leaning Labor opposition working together to try to get legislation past Parliament as soon as next week.

Finance Minister Mathias Cormann, who is overseeing the survey, said the rules would include ensuring appropriate balance in broadcasting.

Labor opposition leader Bill Shorten said the survey needed to have similar protections as political elections on what debate was allowed, and possibly even stronger safeguards.

During election periods in Australia, restrictions are imposed on media advertisements in print, video and online.

"At the moment, the protections in an election... are better than what we have for the survey," Shorten told reporters.

"So we do need to regulate it so that we have some more decent debate than I think we're seeing at the margins," he added.

Heated exchanges among supporters and opponents of gay marriage outside a Brisbane church late Thursday were an early sign of what might be in store.

One woman rallying for same-sex unions told broadcaster Channel Nine the situation turned "extremely aggressive and particularly violent".

Ahead of the court's decision, a poster emblazoned "stop the fags" was put up in Melbourne, while there were flyers describing homosexuality as "a curse of death" distributed in Sydney.

The postal vote will close on Nov 7, with the result known later that month.

If most Australians vote "yes", the government will move for a parliamentary vote, but will not do so if there is a "no" outcome.