Marriage equality advocates have welcomed Liberal senator Dean Smith's "strong and robust" proposal to allow same-sex marriage, in what they say is a exciting moment for their campaign.
"There have been many bills for marriage equality but this is the strongest bill we have seen," Australian Marriage Equality co-chair Alex Greenwich on Sunday told reporters in Sydney.
"It is a bill that is designed to pass the senate.
"Now we need parliament to work together to cross party lines and to achieve marriage equality together."
Mr Smith and MPs Warren Entsch, Trevor Evans, Tim Wilson and Trent Zimmerman have circulated the private members' bill to colleagues ahead of a party room meeting on the issue on Monday.
The Human Rights Law Centre says the bill allows same-sex couples to access to civil marriage while respecting religious beliefs.
"It's important to remember that religious ministers can discriminate now and nothing will change under this bill," director of legal advocacy Anna Brown told reporters in Sydney.
However, a new category of celebrant would give same-sex couples "the dignity and certainty of knowing that when they go to a civil marriage celebrant, they will be not refused service," she said.
The Human Rights Law Centre in a statement added the bill would create a new category of military officer to allow members of the Australian Defence Force - who can only be married by a military chaplain - a secular option.
The coalition promised a plebiscite on same-sex marriage but has also floated the alternative of a postal vote.
Ms Brown and Mr Greenwich said a parliamentary vote was the only way forward.
"This should not be anything that is controversial," Mr Greenwich said.
"This is all about letting loving, committed couples access to civil marriage while respecting the religious celebrating of marriage."
Meanwhile, the Catholic Church says the proposed bill would not protect the religious freedom of Australian people.
"If passed, a bill like this would have grave consequences for all people of faith," Sydney Archbishop Anthony Fisher said in a statement.
"The free exercise of religion is a right afforded to every Australian, and a law which does not protect religious freedom for all people does not protect religious freedom at all."