The government’s plebiscite on same-sex marriage is unlikely to get off the ground, with the Greens announcing they will vote against its establishment.

Their stand follows Opposition Leader Bill Shorten this week hardening his language against the plebiscite. Labor has yet to announce a final position, while crossbenchers Nick Xenophon and Derryn Hinch are opposing it.

Greens leader Richard Di Natale said the party had resolved to vote against the legislation to set up a plebiscite, no matter what that legislation looked like. “We should never put questions of human rights to an opinion poll,” he said. “The Greens won’t support this waste of money that is designed to delay equality and give a megaphone to hate and homophobia.”

He called on Labor and other crossbenchers also to reject the plebiscite legislation.

Di Natale said the best way of ensuring marriage equality was through a parliamentary vote, which could be done next week when parliament resumed if Malcolm Turnbull decided to show some leadership.

The Greens spokeswoman on LGBTIQ issues, Janet Rice, said: “We have listened to the LGBTIQ community, 85% of whom are opposed to a damaging and unnecessary plebiscite because of the harm that it would do.”

Labor will bring forward a motion or private member’s bill on same-sex marriage early in the new parliament. But the government, having taken the plebiscite to the election, will not allow the question to be settled in the parliament.

The plebiscite emerged under Tony Abbott’s leadership and was seen as a tactic by Liberal Party conservatives to delay the issue. Its likely defeat in the Senate represents a win for the conservatives, given there is apparently no prospect of getting change through parliament in the foreseeable future.