The process for a historic free vote on same-sex marriage is now formally underway in Federal Parliament after Australians delivered a resounding Yes vote in the national postal survey.

Key points: 7.8m Yes responses, 4.9 million No

7.8m Yes responses, 4.9 million No 12,727,920 people responded, representing 79 per cent of eligible Australians

12,727,920 people responded, representing 79 per cent of eligible Australians Malcolm Turnbull says "overwhelming" result means Parliament now has to get on with legislating

Malcolm Turnbull says "overwhelming" result means Parliament now has to get on with legislating Check out the full results, including state and electorate breakdown

More than two months after survey forms began arriving in mail boxes and longer still since the Yes and No campaigns kicked off, ABS chief statistician David Kalisch revealed the decision: "61.6 per cent of clear responses were yes".

It was part of a larger statement but it was enough to prompt emotional celebrations at Yes events around the nation.

Confetti and rainbow flags flew in the air, couples hugged and kissed. Many cried with joy.

At some events people proposed to their partners.

A couple gets engaged at the Yes event at Price Alfred Park in Sydney. ( ABC News: Riley Stuart )

Friends Paul Keith and Kevin Roadknight joined the thunderous applause in Melbourne. ( ABC News: Margaret Burin )

There were also scenes of jubilation inside Parliament House.

Labor's leader in the Senate, Penny Wong, was moved to tears.

Sorry, this video has expired Penny Wong reacts after the same-sex marriage survey yes result

On the other side of the debate, most seemed to accept the outcome.

No campaigner Lyle Shelton, from the Coalition for Marriage, called it a disappointing result but said his group accepted and respected the decision of the Australian people.

He said his focus would now be on fighting for parents' rights and fighting for freedom of speech and belief.

Sorry, this video has expired No campaigner Lyle Shelton congratulates the yes campaign

Former prime minister Tony Abbott said the Parliament should "respect the result".

'Your relationships are equal to everyone else': PM

Almost 80 per cent of Australians voted in the national poll.

The strongest vote in favour of gay marriage was in the ACT, where 74 per cent of responses were for yes, followed by Victoria with 65 per cent, then Tasmania and WA with 64 per cent.

New South Wales had the lowest Yes vote with 58 per cent of people backing change and 42 per cent opposing it.

Prime Minister Malcolm Turnbull said the votes were "overwhelmingly" in favour of gay marriage and hailed it as a great moment in Australian history.

"This is just a great day, such a joyful day," Mr Turnbull told commercial radio.

"The overwhelming majority of Australians have reached out and put their arms around same-sex couples and said, 'We love you, we respect you, your relationships are equal to everyone else'."

He predicted he would attend many same-sex weddings after Parliament changed the law.

"There will be stacks of people who will get married. Lucy and I have been asked to come to so many weddings next year when this goes through the Parliament," Mr Turnbull said.

Sorry, this video has expired Malcolm Turnbull says same-sex marriage result is 'unequivocal and overwhelming'

Labor leader Bill Shorten said Australians had voted for a "generous view of themselves, for a modern Australia, where diversity is accepted, supported and respected".

But the survey result delivered a strong note of warning for the Labor Party.

In the western suburbs of Sydney, many Labor-held seats voted heavily against allowing same-sex marriage.

Debate shifts as bill introduced

Sorry, this video has expired Liberal senator Dean Smith introduces legislation to legalise same-sex marriage

With Australians having voted, Mr Turnbull said it was now up to Parliament to "get on with it".

But the debate over the details has a long way to go.

On Wednesday afternoon, Liberal senator Dean Smith introduced the bill to legalise same-sex marriage.

Attorney-General George Brandis moved the bill into the Senate, noting that it would be open for free debate and there was no Government position on the bill.

Senator Smith's bill, which has cross-party support, contains provisions so that ministers of religion cannot be forced to conduct same-sex marriages.

But Senator Brandis said he wished to move two amendments to the bill: to extend religious protections to civil celebrants and that nothing in the bill would make it unlawful for people to hold and express their own views on same-sex marriage.

Senator Wong made a short statement after Senator Brandis announced the bill, asking her colleagues to keep in mind the public's view when discussing amendments.

"We have the view that the Australian people voted to lessen discrimination and not to extend it," she said.

Greens leader Senator di Natale noted the bill introduced to the Parliament was not the bill his party would have introduced themselves, and they would not be open to further discussions regarding "entrenching discrimination in legislation".

Greens leader Richard Di Natale was overjoyed at the same-sex marriage result. ( ABC News: Jed Cooper )

Earlier Finance Minister Mathias Cormann, who is a leader from the conservative side of the Liberal Party, said the Smith bill was a good starting point but needed "additional religious protections".

Another bill proposed earlier this week by Victorian Liberal James Paterson allowed much wider exemptions from discrimination laws, including for service providers like bakers and florists.

But Senator Paterson released a statement on Wednesday afternoon saying he was happy for Senator Smith's bill to take precedence.