Axed cabinet minister Eric Abetz and other conservative coalition MPs have dumped on an "ambush" proposal to legislate same-sex marriage, but make it contingent on a public vote.
Liberal MP Warren Entsch is calling on Prime Minister Malcolm Turnbull to allow parliament to amend the Marriage Act, but leave it to a plebiscite to ratify any changes.
"I have said to him that I think we need to be looking at progressing this issue," Mr Entsch told ABC radio on Thursday.
"Generally, a plebiscite was not generally binding. In this case, it would be binding and that would become law."
Senator Abetz dismissed his colleague's bid as "singularly unhelpful".
"It seems a bit of a thought bubble and an ambush to boot," he told ABC TV.
"As far as I'm concerned, it would be seen as a breach of our election policy to the Australian people in 2013."
Mr Entsch said his plan to trigger legislation would give Australians more power over the process.
"(If) they vote `yes', there is no further process, there is no further debate in the parliament," he said.
Australian Marriage Equality spokesman Rodney Croome was concerned about whether it was constitutionally possible for the current parliament to bind the next parliament.
Nationals senator Matt Canavan agreed, even though he saw some merit in Australians knowing what they would be voting for.
"I think it's right and proper that we take the view with eyes wide open about all the potential changes," he told ABC radio.
Senator Canavan, an opponent of same-sex marriage, was prepared to accept the verdict of the people, as was Senator Abetz.
Nationals MP Andrew Broad said any attempt by the parliament to determine a position before asking the people would be "frankly strange".
That sentiment was echoed by Liberal Dennis Jensen, who said the idea was "messy" and would create a strange situation if the public voted "no".
Labor senator Doug Cameron labelled Mr Entsch's call "a bit bizarre", saying there was no need for a plebiscite when parliament could simply make a decision.
"If Malcolm Turnbull had any backbone ... he would simply say, `Let's have a vote on this and let's treat every Australian equally'," he told reporters.
Mr Entsch is consulting Attorney-General George Brandis about his proposal.
It will be taken to a joint meeting of the coalition parties before being considered by cabinet.
Opposition Leader Bill Shorten reiterated Labor's reservations about a plebiscite.
"Do you really want to see government-funded campaigns attacking the moral basis of same-sex marriage and of your choices about your sexuality?" he told reporters in Canberra.
"I don't think that is a genie we should let out of the bottle - where a whole lot of people are able to stigmatise each other."
Instead Liberal MPs should be given a free vote in parliament, Mr Shorten said.
