Gay law reform advocates have welcomed the move and expect the issue to be debated at this week's ALP national conference.

The state conference motion from Young Labor yesterday was supported by about two-thirds of the delegates.

The motion calls for the Federal Government to reform the Marriage Act to allow same-sex couples the right to marry.

Australian Young Labor president Stuart Benson yesterday noted that the Rudd Government had already recognised same-sex de facto couples, but said more was required to ensure equality.

"We believe a couple is a couple and marriage rights enjoyed by heterosexual couples should be afforded to all couples," Mr Benson said.

Labor Senator Helen Polley spoke against the motion.

She said the Federal Government had gone far enough in economically supporting those in same-sex relationships.

Senator Polley said same- sex marriage "is not an issue in the community any more than what it was 10 years ago".

But Tasmanian Gay and Lesbian Rights Group spokesman Rodney Croome said 80 per cent of same-sex couples supported same-sex marriage.

Mr Croome said it was the first time a state branch of the Labor Party had passed a vote for same-sex marriage.

"It is a really important step forward. Up until now both major parties have uniformly opposed same-sex marriage," Mr Croome said.

Mr Croome expected the issue to be debated at the end of the ALP national conference in Sydney on Thursday.

The Financial Review and Sydney Morning Herald last week reported cross-factional group Rainbow Labor had been lobbying national conference delegates to support gay marriage or civil unions.

Nationally, the ALP supports state-based civil unions - which have been performed in Tasmania since 2004 - but opposes same-sex marriage.

"The decision today in Hobart will send a very strong message to the national conference that it needs to seriously debate the issue and it sends a strong message to Kevin Rudd that he's out of step with not only community opinion but opinion within his own party," Mr Croome said.

ALP state secretary John Dowling said same-sex marriage was not on the national ALP conference agenda but could be debated if a delegate sought to amend the national platform.

Although same-sex marriage reform was resoundingly supported yesterday, Mr Dowling said Tasmanian delegates to the national ALP conference were not bound by the vote.