Prime Minister Malcolm Turnbull, right, and Attorney-General George Brandis. Credit:Janie Barrett "The PM announced that ages ago, that there would be a binding plebiscite. The details of how it's constructed and the question and all of those sorts of things - that's still detail to be worked through and that goes through the normal cabinet process. "There was a bit of conjecture around the timing," the Treasurer acknowledged during his weekly interview with 2GB's Ray Hadley. Senator Brandis surprised colleagues on Sunday by telling Sky News the plebiscite, agreed to under Tony Abbott's leadership, would take place this year under a re-elected Coalition government. If supported by the people, a change to the Marriage Act would be legislated "by the end of the year", he expected. Because of the amount of time necessary to hold a national vote, the comments were widely seen as spilling the beans on a rumoured July 2 early election.

Treasurer Scott Morrison. Credit:Alex Ellinghausen But the promise was quickly kiboshed by the Prime Minister's office, which released a statement guaranteeing only that a plebiscite would be held "as soon after the election as can be done". On Monday, Senator Brandis appeared to backtrack from his earlier timeline, but insisted he had not gone out on a limb. "I don't think there was a disparity whatsoever," he said. "I said we want to have this by the end of the year. Malcolm Turnbull said he wanted it to be as soon as possible after the election. I don't think those are inconsistent positions." Senator Brandis is a strong supporter of same-sex marriage, while Mr Morrison is firmly opposed.

Conservative backbenchers were angered by Senator Brandis' apparent freelancing, as well as the confusion and dysfunction it signalled within the government. South Australian Liberal MP Tony Pasin told Fairfax Media he was taken aback by Senator Brandis' undertaking. "I was certainly surprised to hear that there was seemingly a commitment to conduct a plebiscite this year knowing that there's a very real prospect the election itself wont occur until late in the year," he said. Nationals MP David Gillespie said he had only learnt of the conflict by reading Monday's newspapers, and cautioned against reading too deeply into "spur of the moment" comments in a television interview. Tasmanian senator Eric Abetz told The Australian he "looked forward to being told the detail" about the plebiscite. "These are matters that the partyroom still has to sort out," he said. Mr Morrison also fanned further confusion about the plebiscite by stating "we're not going to bind our members" despite calling it a "binding plebiscite". Coalition members are typically able to cross the floor and vote on their conscience on all motions. Senator Brandis also affirmed on Sunday that he expected MPs would be given a free vote.

"I think it would be perfectly understandable why a member representing a conservative electorate and having conservative views themselves, might choose to vote 'no', and I don't have a problem with that," he said. "But I would expect that there is little or virtually no doubt that if the public vote yes, the Parliament will follow." Labor seized on the confusion by reiterating its promise to introduce a bill in favour of marriage equality within 100 days of taking office. Shadow attorney-general Mark Dreyfus called for the government to abandon the "wasteful and divisive" plebiscite that will cost about $160 million. Follow us on Twitter