But the Senate would not allow the so-called plebiscite, which would have cost £97m, and the result could have been ignored by politicians when deciding how to vote on gay marriage legislation in parliament.
"Marriage equality is about real people, our friends and family, teammates and work colleagues who just want the same dignity as everyone else", Anna Brown, co-chair of the Equality Campaign, said in a statement.
In June 2015, Federal Member for Gippsland Darren Chester became the first Nationals MP to support same-sex marriage.
The announcement came days after a poll showed that the issue of same-sex marriage was wearing thin on voters, who overwhelmingly said they wanted the issue dealt with before the end of the year.
Turnbull also fended off criticism regarding the plebiscite method which is expected to cost more than 120 million Australian dollars (95 million US dollars) to run.
The government can then apparently "second" Australian Electoral Commission officers to the ABS, so the two departments are essentially working together.
Members of Australia's ruling party on Monday blocked efforts to allow a conscience vote in the country's parliament on whether to extend marriage rights to same-sex couples.
Advocacy group Australian Marriage Equality has legal advice it says confirms a postal vote would be unconstitutional, warning of a High Court challenge to prevent it going ahead.
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Voters would have until November 7 to return their ballot papers but voting would not be compulsory.
Details of the vote have been announced today by the Turnbull government. He added, "I'm a strong leader".
Tasmanian crossbench senator Jacqui Lambie, who voted in favour of the plebscite last November, said she would not support a postal vote.
He blasted both sides of politics, saying Opposition Leader Bill Shorten was "determined to wedge (Malcolm) Turnbull to ensure marriage reform is delayed until he himself is the one who gets to sign off on it".
On Monday, Turnbull reportedly cautioned cabinet colleagues over the encouragement of some backbenchers to launch a bill that would have pushed for a free vote on gay marriage. "Strong leaders carry out their promises, weak leaders break them", he told reporters.
Mr Turnbull is a personal supporter of same-sex marriage, but during his own leadership bid gave private assurances to his party's anti-LGBT lobby that he would stick by the plebiscite plan. The upper house Senate rejected a government proposal on the issue, stating a free vote in parliament was the best way of dealing with the matter.
"This is more about the fear and naivety of non-gay people than anything to do with the problem of gay marriage".
A non-binding, non-compulsory postal vote is complete BS, ' Stefanovic said, stressing that the issue should be resolved in Parliament.
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