Thousands of people rallied in Melbourne on Saturday to protest Australian Prime Minister Tony Abbott's decision not to allow a free vote on a gay marriage bill.

The decision by Abbott's ruling conservative coalition effectively doomed the legislative proposal.

Abbott promised to hold a public vote on legalizing such unions if his government is re-elected next year. Critics, however, point out that such votes are not binding.

“Plebiscites are not binding, there is no time frame with a plebiscite, and the danger if the Greens and Labor back this plebiscite move, is that if the outcome at the election is not favorable, then Labor would possibly have to be bound by the plebiscite,” Anthony Wallace from Equal Love told the crowd.

“So, I tell Tony Abbott: Stick your plebiscite where the sun don't shine,” he added.

Federal Opposition Leader Bill Shorten called a popular vote on the issue unnecessary.

“As for a plebiscite, that will be a $150 million tax-payer funded opinion poll to tell us what we already know – we want marriage equality now,” he said.

Polls show a majority (72%) of Australians support marriage equality.