Vote to be held on same-sex marriage this year under government proposal

The Coalition government will resubmit a bill to parliament proposing a plebiscite on same-sex marriage, with a postal vote to be held if the legislation is rejected by the Senate. 

Prime Minister Malcolm Turnbull today confirmed the legislation would be presented this week for a second time. 

"Strong leaders carry out their promises. Weak leaders break them. I'm a strong leader," the prime minister told reporters in Canberra, sticking by the plebiscite policy he took to the 2016 election.

Mr Turnbull said the Australian Bureau of Statistics would run the $122 million postal vote, should the Senate reject the plebiscite proposal as expected. 

Opposition Leader Bill Shorten today said Labor would not support the plebiscite and had not seen details on a possible postal vote. 

"Our view hasn't changed. We think this is a harmful debate," Mr Shorten said.

"We think we should get on with it and vote with it here." 

If the legislation is not passed and the subsequent postal ballot comes back with a majority "yes", a private member's bill would go to parliament, with Liberal members exercising a free vote on it.

The prime minister said the plebiscite and postal vote plan would allow "all Australians to have their say".

"We all know what happens to governments that break their promises," Mr Turnbull said.

"We have made a very clear commitment here and we will stick to it."

Acting Special Minister of State Mathias Cormann said the government will not allow a private bill to be put to parliament if a majority of Australians voted no.

Seven Liberal MPs supported a free vote on the issue during a party room debate yesterday.

One of those, backbencher Warren Entsch, is reserving his right to cross the floor of parliament to vote against the government but has vowed to give the plebiscite a go.

"I'm not so much focused on the process. I want to get an outcome. And whatever it takes to get that outcome, I'm prepared to give it 100 percent," he told the ABC's 7.30 program yesterday.

Advocacy group Australian Marriage Equality has legal advice it says confirms a postal vote would be unconstitutional and warned of a potential High Court challenge.

Mr Turnbull said he and his wife Lucy would both vote to allow same-sex couples to marry.