Support for same-sex marriage is set to be tested in the Victorian Parliament, with both houses to vote on the issue.

The Sex Party will move a motion in the upper house early next year calling on the federal government to change marriage laws to "better reflect equality".

The Greens have also moved a notice of motion in the Victorian lower house to support marriage equality and urge the federal government to amend the Marriage Act and abandon its proposed plebiscite.

Sex Party MP Fiona Patten said a vote in favour of same-sex marriage would send a strong message to the Turnbull government even though the state Parliament could not change the marriage laws.

"It's a lobbying technique," she said.

Australian Sex Party leader Fiona Patten. Photo: Eddie Jim

The plan to introduce the motion into Victoria's upper house comes after the Tasmanian Parliament threw its support behind marriage equality last month.

In Tasmania the motion was introduced by the Greens but gained the support of Liberal Premier Will Hodgman and Deputy Premier Jeremy Rockliff.

The Sex Party motion says marriage equality is a "fundamental step in ending discrimination" against gay, bisexual, transgender and intersex (LGBTI) people.

Ms Patten said it would be a powerful vote of support for the LGBTI community if the Victorian Parliament endorsed same-sex marriage.

The motion rejects Prime Minister Malcolm Turnbull's insistence that a plebiscite should held on same-sex marriage although he has expressed personal support for the change.

"Why on earth does this require a plebiscite?" Ms Patten said. "It doesn't. Polls show strong support."

The motion said a plebiscite would be "potentially damaging" for children of same-sex parents and young LGBTI Australians.

Equality Minister Martin Foley said the state government strongly supported marriage equality for LGBTI Victorians who had a "right to live their lives free of discrimination".

Mr Foley said he was yet to see the Sex Party's motion but would consider "any such motion" on its merits.

Opposition equality spokesman David Davis said he personally supported marriage equality but noted there was a range of views within all parties. Mr Davis said the Coalition would examine the Sex Party motion when it was presented.

Opposition Leader Matthew Guy has previously voiced his support for same-sex marriage, saying his federal colleagues should be allowed a conscience vote.

Victorian Gay and Lesbian Rights Lobby co-convenor Sean Mulcahy said thousands of same-sex couples were denied the freedom to marry in Victoria.

"We have campaigned for many years on the issue of marriage equality and have long called on the federal government to change the definition of marriage under the Marriage Act," he said.

In Victoria 16 local councils have passed motions in support of same-sex marriage, Mr Mulcahy said.

Four state and territory governments have formally declared their support for same-sex marriage.

"It's time for Victoria's Parliament to send a clear message to Canberra in support of marriage equality," Mr Mulcahy said.