GAY marriage campaigners were celebrating last night after Tasmania's lower house became the first chamber of an Australian parliament to pass a bill to legalise same-sex marriage.

The bill, co-sponsored by Labor Premier Lara Giddings and Greens leader Nick McKim, passed by 13 votes to 11.

Tasmania Premier Lara Giddings co-sponsored a bill to legalise same-sex marriage. Credit:Alex Ellinghausen

Labor MPs had a free vote on the bill. All but one, Michael Polley, voted with Green MPs in support of the bill.

The house's 10 Liberal members were bound by the party's position to vote against the bill.