A majority of voters in six seats held by Liberal MPs - whose positions on marriage equality are undeclared - support same-sex marriage and a free vote in parliament, according to new polling.
However, Liberal voters in each electorate are significantly less inclined to believe same-sex couples should be able to wed, or that the government should resolve the issue through a free parliamentary vote.
The ReachTel poll, commissioned by activist group GetUp, underscores the challenge facing Liberal MPs as they prepare for a special partyroom meeting in Canberra on Monday to plot a path forward on the issue.
Voters in the Queensland seats of Moncrieff and Ryan, and in the Western Australian electorates of Hasluck, Stirling, Swan and Tangey were asked for their views.
More than 50 per cent of respondents in five of the six seats supported same-sex marriage.
In Sterling, a metropolitan Perth seat held by Justice Minister Michael Keenan, 48 per cent supported gay marriage, with 42 per cent opposed and 10 per cent undecided.
A majority of voters in each electorate believed the government should hold a free vote in parliament as soon as possible.
Liberal voters were far less likely to support marriage equality and were generally split over holding a free parliamentary vote on the issue.
Respondents were not asked about holding a same-sex marriage plebiscite before changing marriage laws.
GetUp campaigner Sally Rugg described the six MPs - Mr Keenan, Trade Minister Steve Ciobo, Assistant Health Minister Jane Prentice, Aged Care Minister Ken Wyatt, and backbenchers Steve Irons and Ben Morton - as key blockers of a free vote.
"People across these key electorates are fed up with their local MPs sitting on the fence when it comes to marriage equality," Ms Rugg said on Saturday.
"While these MPs continue to dodge the issue and hide they are standing in the way of people marrying the person they love."
Ms Rugg urged the MPs and the rest of the Turnbull government to hold a vote in parliament on marriage equality as soon as they return next week.
Federal cabinet has reaffirmed support for a national vote to decide on same-sex marriage.
However, Western Australian Liberal MP Dean Smith describes the plebiscite as a "tool for delay" and says the time has come for a parliamentary vote.