SAME-sex marriage could cost Malcolm Turnbull at the next election if the issue isn’t dealt with this term, according to a new poll that shows a quarter of Coalition voters could jump ship over the issue.

Twenty six per cent of Coalition voters who responded to a Galaxy Research poll taken last week said they would be likely to support a change in government if marriage equality laws were not dealt with before the next election.

While half of the respondents said marriage equality wasn’t an issue that would affect their vote, another 40 per cent said they would back a change in government over it.

Ten per cent said they would be less likely to vote for a government that allowed a free vote on marriage equality.

The poll, which was commissioned by lobby group Parents and Friends of Lesbians and Gays and canvassed 1000 people across Australia, also showed support for a plebiscite on same sex marriage has dropped to 27 per cent.

Support for a voluntary postal vote, a proposal being considered earlier this year, dropped even further to 14 per cent, while more than 70 per cent of respondents said they wanted politicians to vote on the issue now.

PFLAG spokeswoman Shelley Argent said the Turnbull Government needed to act or risk losing government at the next federal election.

“Mr Turnbull doesn’t seem to understand voters are tired of the political games relating to marriage equality,” she said.

“Our sons and daughters deserve better than the endless delays and indifference we are seeing at the moment and it seems from this poll that most Australians agree.”

Labor, the Greens and crossbench senators joined forces to block the Coalition’s proposal for a $170 million plebiscite in November.

Marriage laws are unlikely to be changed until at least 2019 unless the Coalition changes its stance to allow for a method other than a plebiscite.