The Senate has voted against holding a popular plebiscite on marriage equality and urged the Prime Minister to allow a free vote on the issue before the end of the year.

Greens spokesperson on LGBTI issues and marriage equality, openly gay senator Robert Simms, introduced the motion to parliament calling for the plebiscite to be rejected.

Simms suggested momentum for marriage equality continues to grow and said Australians want a fair go for all.

"Today the Australian Senate rejected a divisive and costly plebiscite and instead called on the Prime Minister to grant a free vote on marriage equality,” Simms said.

“Australians don’t want another opinion poll on this issue. They want the Parliament to legislate.”

The motion passed "on the voices" with no precise count taken of who was for or against but a clear majority was in favour of the motion.

The NSW and WA governments have already rejected the notion of a plebiscite and urged the federal parliament to legislate on the issue.