Maintaining that young lives would be at risk if the question of gay marriage were put to a plebiscite, the Greens took a stand on Friday to oppose any such move.  It puts pressure on Labor to join the Greens in opposing the plebiscite.

"No matter what the enabling legislation for a plebiscite looks like, the Greens will vote against it.  We should never put questions of human rights to an opinion poll," said Greens leaders Richard Di Natale said in a statement.  "The easiest, simplest, quickest, most effective, least costly and least harmful way of ensuring equality in marriage is through a vote in the parliament, and we can do that next week should the Prime Minister decide to show some leadership."

On ABC News Breakfast Mr. Di Natale said the plebiscite was a bad idea and it would unleash hate speech in the community.

"We'll see young kids harm themselves.  I mean, we're speaking to people in the sector right now who are worried that we'll see young people take their lives on the back of a hateful and divisive debate in the community," he said.  "That's what we're elected to do as parliamentarians.  It should be settled in the parliament."

There's also the question of expense.  The federal government claims a plebiscite campaign and vote would cost the public around $160 Million.  But an independent assessment by PricewaterhouseCoopers puts the number somewhere closer to $525 Million.

Labor leader Bill Shorten has leaned away from the plebiscite, calling it the second-best option - but he hasn't ruled it out.  With the Greens and Nick Xenophon (apparently) against it, the government would need Labor to pass a plebiscite.

But some of the Liberals are warning that Gay Marriage in Australia would be delayed for at least a few years and possibly indefinitely if Labor backs the Greens.  Earlier this week, MP Trevor Evans said there was a "very real prospect" marriage equality would not be delivered for three years or more if the plebiscite was blocked.  And Victorian Liberal MP Russell Broadbent said if Labor killed the plebiscite, the coalition would block a parliamentary vote.