Rainbow nation: Same-sex marriage finally passed

Thirteen years after changing the Marriage Act to explicitly forbid same-sex unions, federal politicians voted to undo the last major piece of discrimination against gay and lesbian Australians.

It followed last month's emphatic resolution of the Australian public in the postal survey to join the rest of the English-speaking world by embracing marriage equality.

The vote in the House of Representatives, minutes before 6pm on Thursday, came after last week's vote in the Senate, meaning the law has now passed both houses of Parliament.

Fairfax Media understands a special meeting of the Executive Council has been called for Friday morning for the Governor-General to officially sign the bill into law.

Only four MPs voted against the change, and so clear was the result that a formal count was not required. A handful of MPs - including former prime minister Tony Abbott - chose to abstain.

When the vote was declared on the floor of the House, the packed public gallery exploded into cheers and applause, while MPs crossed the chamber to embrace each other - and in some cases, cry.

The public galleries sustained rapturous applause for several minutes and eventually burst into a rendition of I Am, You Are, We Are Australian.

Numerous well-known gay and lesbian Australians were present to witness the historic moment, including Olympic swimmer Ian Thorpe and actress Magda Szubanski.

"Many of us older LBGTIQ people never thought we would see this day," Szubanski said earlier from outside Parliament House.

"When we were young, it would have been zero per cent of people who would have voted for marriage equality. It was inconceivable - but today, Australia, you've demonstrated you love us. We love you."

A jubilant Prime Minister Malcolm Turnbull stood at the despatch box just before the final vote and declared it was a "great day" in Australian history.

"It's time for more marriages, more commitment, more love, more respect," he said. "This belongs to us all. This is Australia - fair , diverse, loving and filled with respect for every one of us. This is a great day - it belongs to every Australian."

Opposition Leader Bill Shorten said he was "humbled" by the momentous event and "privileged" to be part of it.

"This isn't about me or the other 150 members of Parliament - it is about Australians and Australia, and the LGBTIQ people and their families and their partners," he said immediately after the vote. "We are telling them: we love you, you're equal."

While gay rights campaigners have fought for marriage equality for decades, the direct path to Thursday's vote began two years ago when the former Abbott government announced it would settle the question of same-sex marriage by a public plebiscite.

Mr Turnbull continued that policy, but it was blocked by opponents in the Senate. The government later opted to hold a voluntary postal survey asking: "Should the law be changed to allow same-sex couples to marry?"

Australians voted "yes" to that question by 61.6 per cent to 38.4 per cent, prompting the government to allow a free vote in Parliament, which passed on Thursday.

Attorney-General George Brandis described Thursday's vote as "a truly historic moment" and advised the law would formally change on Saturday, allowing same-sex couples to lodge a Notice of Intended Marriage from this weekend.

The minimum notice period is one month, meaning same-sex weddings can take place in January.

The four MPs to vote "no" on Thursday were Queensland independent Bob Katter, and Coalition MPs Keith Pitt, David Littleproud and Russell Broadbent.

While the votes were not formally tallied, it was clear in the chamber that 130 to 140 MPs voted "yes".

It followed a long day of debate over proposed amendments to Liberal senator Dean Smith's same-sex marriage bill, most of them put forward by conservative Coalition MPs opposed to change. All amendments were comfortable defeated by Labor, the crossbench and several Liberals including frontbenchers Christopher Pyne and Kelly O'Dwyer.