Australian politicians will ask voters whether gay marriage should be legalised after the Green Party won a motion on the issue.

The party won the motion by 73 votes to 72. It was deadlocked at 72-72 and Speaker Harry Jenkins was forced to use his casting vote.

A poll carried out for gay rights groups last month showed that 62 per cent of the 1,005 people surveyed supported allowing gay and lesbian couples to marry, up from 60 per cent last year.

The Greens are a coalition partner in prime minister Julia Gillard’s minority government. Ms Gillard and her Labor party oppose gay marriage but a number of Labor MPs broke ranks to vote in favour of the motion.

Labor will debate its policy on gay marriage at its conference in 2011. Ms Gillard said recently that she believes marriage should be between a man and a woman.

She told ABC: “I do believe that in our society, with our heritage, with our traditions, with our history, that marriage has a special place and special definition, so I’ve been very clear about that.”

Greens MP Adam Bandt, who introduced the motion, told reporters today: “The Australian parliament has just taken an important step to recognising that love is equal. It’s the first time the House of Representatives has recognised marriage equality.”

An amendment to the Marriage Act in favour of gay marriages has also been introduced by Greens senator Sarah Hanson-Young.

Australian expat Portia DeGeneres, who married Ellen DeGeneres two years ago in California, has criticised Ms Gillard for her stance.

“I always thought Australia would pass this equal rights law . . . long before America would,” she told ABC radio this morning. She added that she was “a little bit disappointed in the new prime minister. But I am hoping Australia will be a leader in this.”