Tasmania's Lower House of Parliament has approved laws recognising same-sex marriages and civil unions registered in other states or countries.

Only three of the 25 Members of the House of Assembly - Liberals Rene Hidding, Michael Ferguson and Jacqui Petrusma - voted against the amendment to the Relationships Act.

Attorney-General Lara Giddings says the changes will remove discrimination for same-sex couples in registered relationships.

"This is really a small step, but a significant and important step for those people who have registered or been through a civil union process elsewhere around the world and want us to recognise that relationship as indeed being in existence," she said.

Gay rights campaigner Rodney Croome has welcomed the bill saying it allows for greater respect for personal unions from interstate and overseas.

"It would be good to see the Tasmanian Parliament revisit the issue of same-sex marriage and recognition of same-sex marriages in Australia, but that's a separate issue," he said.

Liberal MP Michael Ferguson, who voted against the bill, says it is a political tool to get same-sex marriage legalised.

"This bill is much more about making a political gesture toward marriage than addressing any remaining discrimination," he said.

The Liberal Party allowed its members a conscience vote on the bill.

But Ms Giddings has denied the Government's next step will be to legalise same-sex marriages in Tasmania.

"This is about removing another level of discrimination which can be held against people who have a significant relationship that has been registered in another jurisdiction but at the moment is not recognised here in Tasmania," she said.

The bill will now go before the Legislative Council for approval.