Legislation passed through the House of Assembly yesterday also recognises significant relationships from other jurisdictions that are registered under laws similar to Tasmania's Relationship Act.

It means same-sex couples will not have to re-register their relationship to be granted legal rights comparable to heterosexual couples.

The UK and New Zealand already recognise same-sex relationships registered under Tasmanian law.

Tasmanian Gay and Lesbian Rights Group spokesman Rodney Croome said the change would have practical applications, especially in emergency medical situations.

"For example, if a same-sex couple in an interstate or overseas union is travelling in Tasmania and one partner is taken ill, the other can rest assured they will automatically be considered next-of-kin," Mr Croome said.

"A couple in an existing union relocating to Tasmania can also rest assured their relationship will be respected without the need for a long and costly re-registration process."

Liberal MHAs were granted a conscience vote on the issue.

Bass MHA Michael Ferguson, Lyons MHA Rene Hidding and Franklin MHA Jacquie Petrusma were the only MPs to vote against the measure.

The three were the only MHAs to support Mr Ferguson's unsuccessful amendment to prohibit the recognition of overseas same-sex marriages.

Mr Ferguson argued countries that have legalised same-sex marriage should not be considered to have equivalent law to Tasmania.

Attorney-General Lara Giddings said laws would only be deemed comparable after a detailed review.

"... (we are) recognising that they have made a commitment to each other through a legal process that has resulted in a legal document and we will not require them to go through that process again," she said.

The legislation needs Legislative Council approval before it is implemented.