Tasmania has become the first Australian jurisdiction to make gender optional on birth certificates.

The controversial reforms were passed by the state's lower house Wednesday afternoon on the casting vote of Liberal Speaker Sue Hickey, who voted against her party.

The laws also remove the requirement for transgender people to have sexual reassignment surgery in order to have a new gender recognised.

Amendments to the controversial bill were finalised last week after a marathon three-day debate concluded on Thursday night.

The legislation allows 16-year-olds to change their registered gender via a statutory declaration without permission of their parents.

It also removes the requirement for transgender people to have sexual reassignment surgery in order to have their new gender recognised. The reforms were attached to legislation bringing Tasmania into line with national same-sex laws.

"I congratulate those upper-house members who put people before politics and who stood up for equality and inclusion," Tasmanian transgender rights activist Martine Delaney said.

"When historians come to write about how Tasmania adopted the best transgender laws in the nation, and the world, they will say the quietest voices spoke the loudest."

The reforms, brought forward by the state's Labor opposition and Greens, passed the lower house late last year when rogue Liberal Speaker Sue Hickey crossed the floor.

The government labelled the legislation as "deeply flawed" and lacking in consultation.

'"(We) have strong concerns about the unintended legal consequences of the amendments," Liberal MLC Leonie Hiscutt said.

Prime Minister Scott Morrison last year labelled the push to remove gender from birth certificates as "ridiculous", while the Australian Christian Lobby has said the removal of gender on birth certificates was ignoring biological truths.