The report from the legal and constitutional affairs references committee determined that a referendum on marriage was a "redundant" path and that marriage ought not be decided on by a popular vote.

The decision is in direct opposition to the government's policy on marriage equality, which is to have a "people's vote" on the matter after the next election.

The senate committee, chaired by independent senator Glenn Lazarus, recommended that a same-sex marriage bill be introduced into the parliament "as a matter of urgency" and that all members ought to have a free vote on the matter.

Greens senator Janet Rice said that a plebiscite held after the next election would be harmful to LGBTI Australians and their families.

"The only ones suggesting a complicated and prolonged plebiscite or referendum are those who are resigned to being on the wrong side of history," she said.

However, Coalition senators Ian McDonald and Linda Reynolds delivered a dissenting report, writing a plebiscite was the appropriate avenue to deal with the "incredibly divisive social issue".

McDonald also used his additional comments to slam the inquiry itself, labelling it "an absolute and blatant waste of taxpayers money".

The cost of a plebiscite on same-sex marriage is estimated at $158 million, according to the Australian Electoral Commission.