The Turnbull government could still walk away from its plan to hold a plebiscite on same-sex marriage, opening up the prospect of Parliament voting on same-sex marriage before the federal election, Liberal MP Warren Entsch says.

Mr Entsch, who is working with Attorney-General George Brandis to develop the plebiscite, said when details came before the party room, it would give the Coalition the chance to discuss the issue again.

The Coalition's leading advocate for same-sex marriage said when presented with the cost, timeframe and process of a national vote, some MPs may want to revisit the government's stance.

"Would you like to go down this track or would like to also consider the option of a free vote?"

Mr Entsch said recent comments from senators Eric Abetz and Cory Bernardi - suggesting they would not vote for same-sex marriage regardless of what a plebiscite says - may also prompt some MPs to reconsider the plebiscite position.

He said people might be "critical" of the government spending an estimated $160 million on a national vote if some MPs were not going to abide by the outcome, anyway. However, he noted that the votes of a small group of dissenting senators was not likely to make "any difference" when it came to the legislation ultimately passing or not passing Parliament.

Mr Entsch also accused Labor of using the gay community to score political points, when responding to Terri Butler's plan to bring on a parliamentary vote on same-sex marriage.

On Tuesday, the Labor frontbencher said she would attempt to bring the cross-party same-sex marriage bill on for further debate and then a vote "soon". This could be within the next few sitting weeks.

Labor's position is that all MPs should have a free vote and that Parliament does not need a plebiscite to inform its position.

Mr Entsch, who introduced the cross-party bill last August with a group of MPs across Parliament, including Ms Butler, said he would "love to see my bill get up".

But he said his Labor colleague had not informed him of her plans and they would not work.

In order to have a vote, a majority of MPs in the lower house first need to agree to move to this stage of the process - which is unlikely, given the Coalition's lack of a free vote and current policy of holding a plebiscite first.

"I'm a little disappointed with Terri," Mr Entsch said.

"It just destroys the prospect of getting [the bill] up ... she's using the gay community to try and push a political point."

Last August, in a marathon meeting, the Coalition under Tony Abbott decided it would hold a people's vote on same-sex marriage.

While Malcolm Turnbull argued against a plebiscite at the time, since becoming Prime Minister he has stuck by the plan, noting that "the Coalition party room ... made a decision that the matter would be put to the people".

Mr Entsch said this was not inconsistent as Mr Turnbull had made a firm commitment that there would be "no more captain's picks" under his leadership.

The government's plebiscite plans are due to come before cabinet in the next fortnight, after which they will go to the party room for discussion.

This comes as Australian Marriage Equality-commissioned polling found that voters in three Nationals seats opposed the idea of a plebiscite, with more than 60 per cent describing it as "poor" or "very poor value for money".

It also comes as Australian Marriage Equality estimates that if Liberal MPs had a free vote, there are now enough MPs in both houses of Parliament to pass a same-sex marriage bill.

Australian Marriage Equality spokesman Rodney Croome said Coalition backbenchers should "welcome the opportunity to revisit the plebiscite plan, because a lot has changed since it was first adopted".

Mr Croome pointed to the polling, as well as continued divisions within the Coalition.

"A vote in Parliament would cost nothing," he said.

The Australian Christian Lobby argues the $160 million price tag is a "reasonable and necessary price" to settle the issue.

"We need a free and fair debate so Australians can assess the claims of both sides and then make their decision in the privacy of the ballot box free from intimidation and pressure," managing director Lyle Shelton said.

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