The Tasmanian State Parliament will vote Tuesday on a proposed same sex marriage motion, making Tasmania the first Australian state to push for legalised gay unions.

The bill was initially drafted by the Greens. However, it backed out pushing for legislation but instead will initiate the motion which has received support from Tasmanian Premier Lara Giddings, who is also Labor Party leader in the state.

"We'll be moving in the Parliament that the House express in principle support for marriage equality and also that the Federal Parliament amend the federal Marriage Act to provide for marriage equality," Greens leader Nick McKim was quoted by The Mercury.

He explained there remains too much discrimination suffered by same-sex couples, gay people, lesbians and transgendered people in communities, streets and pubs.

"If the Commonwealth Parliament doesn't act in a timely way and we've indicated that we expect action this year, then we will bring our state-based same-sex marriage bills on for debate," Mr. McKim said.

Labor's national conference in December includes gay marriage on the party's agenda, although party leader and Australian Prime Minister Julia Gillard - who is in a de facto relationship with partner Tim Mathieson - is against legalised gay unions. However, there is strong support for same-sex marriage within the party.

Among those expected to support legalised gay union is Finance Minister Penny Wong who is in such a living arrangement with Sophie Allouache. The couple is expecting a child.

Australian federal law does not permit same-sex marriages and does not recognise gay marriages performed in other countries. However, the Australian Capital Territory performs civil partnerships and records the union on domestic partnership registries in Tasmania, Victoria and New South Wales.

With state or federal recognition of gay unions, the partners could be entitled to tax-free superannuation payments, tax, health, social security and other benefits that unmarried straight couples already enjoy.

A survey by Galaxy poll in August showed that 60 per cent of Australians favour marriage equality.