Peter Dutton has backed a proposal for a voluntary postal plebiscite on marriage equality, arguing it fulfils the Coalition’s election promise despite the Senate blocking a compulsory vote on the social reform.

The proposal for a postal plebiscite has been criticised by the Liberal moderate MP Trent Zimmerman and marriage equality advocates, although the MP Warren Entsch has commended Dutton for looking for a way through the impasse on marriage.

On Tuesday Fairfax Media reported that Dutton and fellow senior conservative in cabinet, Mathias Cormann, were pushing the postal vote as a means to resolve the marriage issue before the next election.

At a doorstop interview in Canberra on Thursday, Dutton told reporters the Coalition’s policy was to hold a plebiscite but there was “no prospect of the plebiscite proper passing through the Senate”.

“There is an option, as I understand, in relation to the postal plebiscite ... it adheres with our policy that we took to the last election and I think we need to deal with the realities of the current parliament.”

Dutton said the idea should be considered, and a number of people in “senior roles” were working together to successfully conclude the business of the government.



Later in an interview on 2GB radio, Dutton said the postal plebiscite “doesn’t require legislation”, as far as he understood, and “may achieve in some ways the same outcome to a plebiscite that you would think of in the traditional sense”.

“So I don’t support walking away from our election pledge ... the Liberal party went to the last election with a policy for a plebiscite. We should abide by that.”

At a doorstop in Canberra on Thursday Tony Abbott said he was “confident that what [Dutton] has been trying to do is to secure the best possible way of realising the commitment that we took to the people at the election”.

Abbott said the government had committed that “at least for the life of this parliament the Marriage Act will not be changed without putting it to the people first”.

On Tuesday Zimmerman said a postal vote was the wrong path because it would be seen as “tricky and sneaky”, it would be nonbinding and its result could be disregarded and it would result in a three-month campaign.

But Entsch, another Liberal moderate who supports marriage equality, told Guardian Australia: “I commend [Dutton] for looking at options. I welcome the acknowledgement that something needs to be done.”

Entsch, Zimmerman, and senator Dean Smith support a free vote in parliament this term, and the latter two have not ruled out joining a cross-party bill or bringing their own private member’s bills to force the issue.

Pressure is growing on the government over the issue. The industry minister, Arthur Sinodinos, has joined the call to deal with marriage equality this term, although he did not say whether that should be achieved through a postal plebiscite or a free vote.

Turnbull has never ruled out a free vote but reiterated his personal support for a plebiscite as recently as Friday and again on Wednesday through a spokesman.

The Australians for Equality director, Tiernan Brady, said the postal plebiscite was “not a serious proposal ... [that would] deliver marriage equality in line with the will of the majority of the Australian people”.

Brady said the proposal would be seen as sneaky because it bypassed parliament, which had rejected the plebiscite.

In an opinion piece published on Tuesday, longtime marriage equality advocate, Rodney Croome, warned that a postal plebiscite without legislation would mean there was no parliamentary oversight of the question, the campaigns for and against the proposition, or the voting procedure.

He also argued that while 70% of the Australian people support marriage equality, only 40% of that support is strong, “not enough to win a national ballot by itself”.

“A non-compulsory vote means the 30% of the electorate who are soft supporters of marriage equality are much less likely to vote.”