Senior Liberal Christopher Pyne says it would be political suicide for the federal government to ignore a successful national vote on same-sex marriage.
Three of his coalition colleagues have openly said they won't be bound by the results of a plebiscite, with one labelling it nothing more than a "glorified opinion poll".
But Mr Pyne said it wasn't up to those three senators to decide what becomes law.
"If the government's policy is to hold a plebiscite and implement the outcome, then obviously that would become the law," he told ABC's Radio National on Thursday.
One way that could be guaranteed, he said, is if a plebiscite was used simply to ratify legislative changes to the Marriage Act - an idea initially raised by fellow Liberal MP Warren Entsch.
But Mr Pyne stopped short of endorsing the proposal because it didn't think it was necessary.
"I don't believe that any government or any political party that holds a plebiscite that says 'yes' to marriage equality, or for that matter 'no' to marriage equality, would then disregard the views of the electorate," he said.
"I think that would just be political suicide. I think it's a bit of a moot point."
Dumped cabinet minister Eric Abetz, who is against same-sex marriage, sparked debate by suggesting he might ignore the will of the Australian people.
His views were shared by fellow Liberal senator Cory Bernardi, who reiterated he won't support any change to the Marriage Act regardless of the outcome of a national poll.
"A plebiscite is a glorified opinion poll and no government should be bound by that," Senator Bernardi told Sky News.
"I think there are many members of parliament who are happy to bow to the whims of what is populist public opinion - (but) I've never been one of those."
Nationals senator Bridget McKenzie on Thursday also confirmed she would vote against any bill that came before parliament on the issue, contradicting her colleague Michael McCormack who said he would support the will of the people.
"My conscience on this matter is that I would vote against same-sex marriage," Senator McKenzie told reporters in Canberra after repeated questioning.
But two of Prime Minister Malcolm Turnbull's junior ministers feel differently.
Assistant Minister to the Treasurer, Alex Hawke, despite being a same-sex marriage opponent, said he will respect a potential 'yes' vote in a fair and balanced plebiscite.
"I'd expect most parliamentarians would respect the will of the Australian people one way or the other - and that's why you have a plebiscite," he told Sky News.
"I'm not certain why some people are coming out and saying they wouldn't respect the judgment of the Australian people."
Alan Tudge, assistant minister to the prime minister, said he was absolutely certain if the plebiscite was successful and the coalition re-elected, "then we will get same-sex marriage".
"I think the Australian public can be very reassured about that," he said.