Lib senator to vote against plebiscite

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.

Meanwhile, Greens senator Sarah Hanson-Young confirmed she would be toeing the party line and opposing the plebiscite.

She previously flagged possibly backing a popular vote if it was the only option for marriage equality in this term of parliament.

"I said I would wait to see the government's proposal and now that I have, I won't be supporting it," she said in a statement.