A group of Liberal MPs is hoping to convince colleagues a free vote on gay marriage is the way to go after drafting their own laws that enshrine protections for religious communities.
The private members' bill, supported by Dean Smith, Trent Zimmerman, Warren Entsch, Trevor Evans and Tim Wilson, has been circulated ahead of a special party room meeting on the issue in Canberra on Monday afternoon.
The legislation would allow two people to marry regardless of their sex or gender.
It also would protect all religious ministers and civil celebrants from legal action if they refuse to marry same-sex couples, and covers service providers - such as bakers, florists and photographers - if they can prove their business is linked to a religious body.
"(It's) the most comprehensive bill the parliament has ever had in regards to not only providing for same-sex marriage but, importantly, respecting community attitudes that would like to see religious freedoms protected," Senator Smith told ABC TV on Sunday.
The co-chair of advocacy group Marriage Equality, Alex Greenwich labelled the proposal the strongest they've seen.
"It is a bill that is designed to pass the Senate," he told reporters in Sydney.
The Australian Christian Lobby, meanwhile, criticised the bill, saying the exemptions were extremely narrow.
The five backbenchers want the party room to scrap its commitment to a plebiscite and sanction a free vote in parliament.
Mr Zimmerman hoped the draft bill would convince colleagues, lamenting that much of the debate to date had been about process rather than legislative substance.
Senator Smith insists the push is not a revolt against Prime Minister Malcolm Turnbull and shouldn't be viewed through the prism of leadership.
Manager of Opposition Business Tony Burke gave an "absolute guarantee" to any Liberal member that Labor wouldn't jeopardise their pursuit of a free vote on gay marriage.
"We will not use this issue as an issue of confidence in the government," he told Sky News.
Senator Smith labelled a postal vote - the other alternative being considered - an even worse idea.
Marriage equality advocates have promised to launch a High Court challenge if the idea gets up based on legal advice that the government would need specific legislation to hold a postal vote on the issue and allocate sufficient funds.
Crossbench senator Nick Xenophon - who helped shoot down the plebiscite late last year - said the Smith bill seemed a sensible way forward and he would support it if it got up in the Senate.
"This shouldn't be subject to such contortionism by the Liberal and National parties, we should just get on with it," he told reporters in Canberra.
Hundreds of same-sex marriage supporters attended a rally in Sydney on Sunday, while dozens protested in Melbourne's CBD, calling on politicians to act.