A majority of Australians have voted in support of same-sex marriage after a lengthy and often ugly debate.

After weeks of campaigning, months of planning and years debate, the results of the controversial three-month-long postal survey revealed 61.6 per cent of people voted ‘yes’ and 38.4 per cent ‘no’.

The question asked simply: “Should the law be changed to allow same-sex couples to marry?”

However, the poll, carried out by the Australian Bureau of Statistics, is not legally binding and voluntary, which is not typical in the country.

While it is purely a guide for politicians on how to treat the issue in Parliament, the huge 80 per cent turn-out and the clear majority will put pressure on the Government to act.

Shortly after the ‘yes’ result was revealed, Prime Minister Malcolm Turnbull stated that his goal remained to have legislation to change the Marriage Act passed through the parliament before Christmas.

“It is our job now to get on with it, get on with it and get this done. It is fair,” he told reporters in Canberra.

“The people have voted yes for marriage equality. Now it is our job to deliver it.”

The campaign has been marked by negative campaigning by the ‘No’ campaign that critics have condemned as bordering on hysterical, with conservative politicians lining up with churches fearing religion is under attack.

One advert attacking gay marriage depicted a woman claiming it could lead to her son wearing a dress to school, which was dismissed as “patently ridiculous”.

But a United Nations committee last week criticised Australia for putting gays and lesbians “through an unnecessary and divisive public opinion poll”, and called on Australia to legislate for marriage equality regardless of the survey’s outcome.

What happens now Australia has voted ‘yes’ to gay marriage?

The marriage equality process will then return to Canberra, and require the parliament to agree to allow same-sex marriage.

Prime Minister Malcolm Turnbull has promised that, in the event of a yes vote, his Government “will facilitate a private member’s Bill to make same-sex marriage legal before the end of the year”.

Most of the Parliament has promised to vote ‘yes’ on any parliamentary vote if the result was ‘yes’, so any legislation should easily pass.

However, around 30 per cent of the politicians in both houses either failed to tell pollsters their voting intention or said they had reservations about legalising same-sex marriage, while seven MPs flat out said they would vote no even if the entire country voted yes.

What is the history of the vote?

More than a decade ago, Australia’s federal parliament defined marriage explicitly as a union between a man and a woman, after citizens who had married in Canada sought to get Australian courts to validate them. Battle-lines between traditionalists and progressives have since been drawn.

In 2015, then Liberal Prime Minister Tony Abbott, a same-sex marriage opponent, committed his conservative government to holding a compulsory nationwide vote to decide whether the unions should be legal.

He was replaced weeks later by current Prime Minister Malcolm Turnbull, who supports marriage equality and opposed the public vote but eventually agreed to it in a deal with party powerbrokers.

The Senate refused to fund a compulsory vote, however, so the government opted for a voluntary postal ballot. Critics say it is unlikely to accurately reflect public opinion.

Almost 79 percent of more than 16 million Australian voters posted ballots before the two-month survey closed.

The result will be announced on Wednesday. If a majority calls for marriage equality, Parliament will vote on a bill in the final two-week session of the year.

Passage is by no means certain even if a vote goes ahead.

What did the polls say?

A survey commissioned by Sydney University’s U.S. Studies Center found support for gay marriage was stronger in Australia than in the United States, where it has been legal since 2015.

The poll by survey company YouGov found 60 percent of Australians support same-sex marriage, 32 per cent oppose it and 8 percent were undecided.

In the United States, 48 per cent of respondents supported marriage equality, 40 percent oppose it and 12 per cent were undecided.

The online survey of 1,009 Australians and 1,107 Americans in late October has a 3 per centage point margin of error.