Last week, Greens senator Sarah Hanson-young said she would consider voting for a plebiscite if parliamentary options to achieve marriage equality were exhausted, despite her party's opposition to the public vote.
Greens leader Richard Di Natale has ruled out Greens support for a plebiscite, saying "No matter what the enabling legislation for a plebiscite looks like, the Greens will vote against it".
But Hanson-Young told Sky News, "Nothing isn't an option for me".
"We have to come up with a way forward, what we have right now is a stalemate."
Hanson-Young reiterated that a plebiscite is not her first option, saying, "We should be doing all that we can to get a vote in the parliament".
Australian Marriage Equality co-chair Alex Greenwich says he agrees with Hanson-Young that Australians should not wait for marriage reform.
With the lovely @AlexGreenwich xx
Greenwich and Hanson-Young are friends and attended the parliamentary Midwinter Ball together on Wednesday night.
Greenwich told BuzzFeed News the senator had made it clear marriage equality is an urgent priority for Australia.
"The Greens, including Sarah Hanson-Young, have expressed a great deal of concern over the proposed plebiscite, and that's been expressed in their voting platform," Greenwich said.
"I agree with Senator Hanson-Young that we shouldn't wait for reform."
BuzzFeed News asked Hanson-Young whether she had discussed her stance on the plebiscite with Greenwich. Her office did not respond.
Advocacy group Just Equal, which is focussed on achieving marriage equality without a plebiscite, criticised Hanson-Young's stance.
Spokesperson Ivan Hinton-Teoh said the LGBTI community is largely opposed to a plebiscite and had welcomed the Greens decision to vote against it.
"I urge Senator Hanson-Young to heed the views of the LGBTI community and declare her unconditional opposition to a plebiscite."
The government has currently secured 37 votes in the senate for the plebiscite.
It needs just two other senators from the Greens, the Nick Xenophon Team, Labor or the crossbench for the legislation to pass.