Pressure to draft a plebiscite: Attorney-General George Brandis. Credit:Fairfax Media In what would be a significant concession, numerous sources have told Fairfax Media it is almost certain Senator Brandis will recommend to cabinet that no taxpayer money be given to either side. That would delight the "yes" camp but anger conservatives, given the Australian Christian Lobby has asked for $15 million in public funds. A self-executing plebiscite would also simplify the process. In that scenario, a single bill would propose changes to the Marriage Act that are triggered if, and only if, a plebiscite is passed by a majority of Australians. "It's certainly one of many deal-breakers," Labor's marriage equality spokeswoman Terri Butler told Fairfax Media. "[But] even if you assuage our concerns on that point you've still got a long way to go to convince Labor." Senator Brandis told a Senate estimates hearing in February the self-executing option was being considered. And in July, he said the plebiscite "should be conducted as closely as possible to the manner in which … a constitutional referendum is conducted", which would mean the changes are self-executing.

Constitutional law expert George Williams said a self-executing plebiscite was plausible and "the least-worst thing to do" because "it avoids you having to go back to Parliament again". However, it would upset conservative MPs by denying them the opportunity to vote down same-sex marriage in line with their electorates. Asked whether the self-executing option was still under consideration, a spokeswoman for the Attorney-General said the mechanics of the plebiscite were a matter for the cabinet. "The Attorney-General has engaged in extensive consultations with stakeholder groups on both sides and has met with parliamentary colleagues, including the shadow attorney-general to discuss the issue," she said. Several Liberals who support same-sex marriage are calling on government leaders to reach out to the opposition in a last-ditch effort to save the plebiscite, which would be scuttled by the Senate if opposed by Labor.

Warren Entsch, a veteran advocate for gay rights within the Coalition, said he was "confident" Senator Brandis would engage with Labor to ensure the bill could pass. "He needs to make sure that people are very much aware that there's no ambiguity, that there's no trickiness," he said. "My understanding is that the door is open for further discussions." Tim Wilson, one of a handful of gay MPs to enter the Parliament at the election, told Buzzfeed News that if he were Malcolm Turnbull, "I'd bring in the Labor Party to discuss the legislation." He later told Fairfax Media he believed a number of Senate crossbenchers, including the crucial Xenophon senators, were "playing posturing" and could yet be convinced to support the plebiscite. "It's pretty obvious to everybody that if you want to get something through, you're going to have to negotiate," Mr Wilson said.

Gay Liberal MP Trent Zimmerman said the two parties "definitely need to talk" but "the cabinet and the partyroom need to settle on a position first". That could happen next week when Parliament returns.