A government senator is threatening to help scuttle a plebiscite on same-sex marriage, saying the idea of a national poll is so abhorrent to him that he could not support it.
Dean Smith, the Liberal Party's first openly-gay politician in federal parliament, told Fairfax Media on Tuesday he could not "countenance a proposition that threatens to undermine the democratic compact that has seen Australia emerge as one of the most stable parliamentary democracies in the world".
He will either cross the floor to vote against the bill or abstain from the vote.
Supporters of same-sex marriage fear providing $15 million in public funding for opposing sides in a plebiscite opens up the gay and lesbian community to a summer of hate.
The coalition party room on Tuesday will consider cabinet's decision to hold a plebiscite on February 11 and give $7.5 million each to the two sides of the debate.
Prime Minister Malcolm Turnbull said the government intended to give every Australian a say on the issue.
"We want it to be an absolutely fair, civil contest in which both sides feel they've had a fair go," he told reporters in Canberra.
Mr Turnbull said the only person standing in the way of a plebiscite was Mr Shorten.
"Mr Shorten should stop blocking this democratic process for which we have a clear mandate from the public," he said.
MPs are also expected to endorse the question that will be put to voters: "Do you support a change in the law to allow same-sex couples to marry?"
But a compulsory vote and funding for the plebiscite needs parliament's approval, something Labor's Graham Perrett thinks won't happen.
"All this kowtowing to the extreme right of (the coalition) will all come to nought and be a total waste," he told ABC radio.
"It's got a snowflake's chance in hell of getting through the Senate."
WATCH: PM under fire over same-sex marriage plebiscite funding
Marriage equality advocates says public funding for yes and no cases makes the plebiscite even more unacceptable.
"We cannot countenance taxpayers' money being spent on what is likely to be hurtful, harmful and even hateful campaign materials from the 'no' case," Parents and Friends of Lesbians and Gays spokeswoman Sharyn Faulkner said.
Greens senator Janet Rice is worried the gay and lesbian community now faced a summer of "hateful, hurtful, homophobic" speech.
Deputy Labor leader Tanya Plibersek said those who had advocated public funding - mostly opponents of same-sex marriage - also wanted anti-discrimination and advertising rules suspended.
"What is it that these organisations want to say that is against the law to say right now?" she asked on ABC radio.
The Australian Christian Lobby says public funding would level the playing field but complained $7.5 million apiece was on the low side.
"It's been a very one-dimensional debate about the love of two people but there's been very little discussion about the consequences," managing director Lyle Shelton told ABC radio.
His group intends to campaign on issues such as gender teaching in schools, including the Safe Schools program.
Labor, the Greens and advocates are still holding out hope for a free vote in parliament on same-sex marriage.
Liberal Democrats senator David Leyonhjelm described that as a "heroic assumption".
"Same sex marriage is a bit like a seedling tree, everybody wants to own it," he told reporters in Canberra.
"All the interest groups are like dogs and you know when a dog likes to own territory it cocks its leg on it - they'll all cock their legs on it so much, that they will kill the tree."
Labor playing gay mental health card: MP
Labor has been accused of playing the mental health card over the same-sex marriage plebiscite by a federal government MP.
Opposition Leader Bill Shorten, who introduced private legislation on Monday to make the change without a national vote, has warned if a single young person took their own life because of the plebiscite campaigns that would be one too many.
His deputy Tanya Plibersek reiterated that position on Tuesday, saying LGBTI young people are about five times more likely to have major depressive episodes.
And one survey at least shows they're about 15 times more likely to have suicidal thoughts.
"I don't think it's an overstatement to say we should be concerned about that," she told ABC radio.
"Being a teenager who's coming out during a national debate about whether there's something wrong with you, something wrong with the fact that you love someone of the same gender, that's a terrible thing."
But Liberal MP Andrew Laming said the opposition is being "two-faced" by resisting a public vote.
"These are people with no training in mental health pulling a mental health card for their own political purposes," he told reporters in Canberra.
Dr Laming claimed the regular "failure-to-launch" attempts to have parliament make the change was prolonging the uncertainty.
"So the LGBTI community should be acknowledging that there are definite mental health concerns particularly for young adolescents and the fastest way to resolve this is not to protract it.
"That's precisely what Labor's doing purely for political benefit."
The Australian Christian Lobby was disappointed to hear Mr Shorten doesn't have confidence in his fellow Australians to have a respectful debate.
"We've never put out anything into the public square which has been hateful or denigrating our fellow Australians, nor would we want to," managing director Lyle Shelton told ABC radio.
"To conflate this and to suggest that these sort of things might happen really I think is a new low in Australian politics."
(Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14, Suicide Call Back Service 1300 659 467, MensLine Australia 1300 78 99 78)