She used her casting vote despite a plea from the leader of government business in the House of Assembly, Michael Ferguson, to delay debate of the bill which was amended by the Legislative Council last week.

Related: Transgender community celebrates but Premier threatens to repeal new law

Mr Ferguson sought the delay because Attorney-General is on bereavement leave because of the death of her mother.

"It is the Attorney-General's bill and she is not here and it is important that she be here," Mr Ferguson said.

"This should not be rammed through."

Labor had moved to bring on the bill.

Greens leader Cassy O'Connor said the bill had been "rigorously examined" and should be passed.

"There is no justification for not dealing with it today," she said.

"It is a robust bill.

"Small L Liberals should hang their heads in shame because this is about individual human rights."

Labor's legal spokeswoman Ella Haddad said there had been extensive consultation on the bill.

"The Upper House did a power of work and should be recognised and applauded for protecting the rights of transgender Tasmanians," she said.

"They are very simple changes.

"This government has fuelled the flames of a scare campaign across Tasmania."

Premier Will Hodgman maintained the government considered the bill "flawed" and would continue to oppose it.

"The Legislative Council has completely changed this legislation and shows how badly drafted it was," he said.

"It is entirely unrecognisable. It should go through a full legal review."

The Legislative Council spent three days debating the bill and overhauled it.

The House of Assembly now looks set to pass it making Tasmania the first Australian jurisdiction to make gender optional on birth certificates.

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.