Attorney General George Brandis has released a draft paper on how the Marriage Act could be changed. Picture: AAP/Lukas Coch

The key question is whether Prime Minister Malcolm Turnbull will then allow legislation without a national ballot or suspend all attempts at a law change until the next election.

And Labor will have to face the charge it will have wrecked the best chance yet to change the Marriage Act, and the accusation it was paying politics.

The arm-wrestle is complicated by the fact the leadership of Parliament — Mr Turnbull, Attorney General George Brandis, Opposition Leader Bill Shorten, his deputy Tanya Plibersek — support same sex marriage.

Mr Brandis has released the discussion draft of the legislation which could change S5 of the Marriage Act to replace “a man and a woman” with “two people”.

Mr Shorten will take the legislation to a Caucus meeting and repeat his arguments of the past month that it is divisive, expensive and potentially dangerous to vulnerable homosexuals.

Labor and the Greens are expected to unite against a government Bill in the Senate.

The Coalition has accused Bill Shorten of playing politics. Picture: AAP/Lukas CochSource:AAP

Mr Brandis said the proposed plebiscite in February would be the quickest way towards achieving same sex marriage in this Parliament.

“For those who believe in same sex marriage this is the most immediate and only feasible opportunity to achieve this in the foreseeable future,” he said in a statement.

“The Labor Party did nothing to progress same sex marriage during their six years in government.

“They should not get in the way in Opposition. The government calls on Bill Shorten and the Labor Party to get out of the way, stop the delay and make same sex marriage a reality.”

The government also has to manage concerns from religious groups.

Mr Brandis believes protections for ministers of religion who refused to conduct gay marriage services would be strengthened by the legislation. Marriage celebrants would be able to decline

requests for same sex ceremonies.

However, there would be no special provisions for businesses — such as caterers, cake makers — which refused to serve same-sex weddings.

Couples who wed overseas would have their marriages recognised here. But not if the parties were siblings, in a parent-child relationship, or the marriage was polygamous.