The Federal Government's bid to hold a plebiscite on whether to legalise same-sex marriage has been defeated in the Senate.

Key points: Public vote on same-sex marriage rejected by Parliament

Public vote on same-sex marriage rejected by Parliament Labor, Greens say plebiscite would have sparked hatred towards LGBTI community

Labor, Greens say plebiscite would have sparked hatred towards LGBTI community Nationals MP says Coalition will not have conscience vote on issue

The proposal was voted down on Monday night in the Upper House 33 votes to 29.

The Attorney-General George Brandis had warned a defeat would result in delaying same-sex marriage in Australia for years to come.

But the Federal Opposition says the plebiscite would have resulted in harmful debate against the gay and lesbian community and want a direct vote in Parliament, instead.

Labor and the Greens were joined by the Nick Xenophon Team and Derryn Hinch to defeat the bill, while the Coalition secured the support of the One Nation Party, the Liberal Democrat senator David Leyonhjelm and Tasmanian senator Jacqui Lambie.

Liberal senator Dean Smith abstained from voting in Parliament late on Monday night.

It ends 14 months of debate over the fate of the plebiscite, which was first proposed by the former prime minister Tony Abbott and taken by his successor Malcolm Turnbull to the 2016 federal election.

The Federal Government said it was the quickest way to achieve same sex marriage, promising a plebiscite would be held in February 2017, with Mr Turnbull confident it would be supported by the public.

But the Federal Opposition, joined by an increasing number of gay and lesbian groups, argued it would result in divisive debate that would have hurt vulnerable members of the community.

It also attacked the proposed $170 million price tag for the plebiscite.

Brandis hits out at Labor

Attorney-General George Brandis earlier criticised Labor for opposing the plebiscite.

"Stop playing politics with gay people's lives, because that is all that you are doing," Senator Brandis told Parliament.

"A vote against this bill is a vote against marriage equality."

"And those who claim to believe in marriage equality, but nevertheless, for their own cynical, game-playing reasons, are determined to vote against it, should hang their heads in shame."

Sorry, this video has expired Brandis attacks Labor over plebiscite rejection

Labor senator Louise Pratt described the plebiscite as "an utterly demeaning act."

"No child should have their family status a subject of public debate like this."

LGBTI community lobbied against plebiscite

Greens senator Rachel Siewert said the gay and lesbian community had lobbied strongly for the plebiscite bill to be defeated.

"I've lost count of the number of my LGBTIQ friends who have urged and begged us not to support this plebiscite."

Chair of Australian Marriage Equality Alex Greenwich said supporters of same sex marriage should refocus efforts on a direct vote in Parliament to change the Marriage Act.

"We know that a majority of Australians, indeed a majority of parliamentarians, support this reform."

"We hope that we can all work together to finally get this through our Parliament."

No same-sex marriage until at least 2019?

Nationals MP Andrew Broad says the Government would not revisit same-sex marriage for the foreseeable future, saying that the plebiscite was the only pathway towards marriage equality.

"If the Labor Party wants to block that (the plebiscite) then there will be not vote on same sex marriage for this term, and I anticipate that will probably be our policy heading into another term of Government," he said.

Mr Broad said there would not be a conscience vote offered to Government MPs and senators on this issue.

"I don't think that's going to happen," he said.

"The Coalition's position was determined by the party room, it remains our position."

Mr Turnbull has not yet spelled out what he would do if the plebiscite was voted down.

But Mr Broad said the Prime Minister was committed to the plebiscite, despite arguing against it when it was initially made Coalition policy.

"I actually believe that the Prime Minister believes in the Australian's right to decide this one," Mr Broad said.

"He's very much firmed in that position."