For Tasmanian politician Cassy O'Connor, changing the laws to give parents the choice of whether they list their child's gender on a birth certificate is a personal crusade.

"Every parent wants their child to be happy, that is the driving motivation. We just want our kids to be happy," the leader of the state's Greens said.

Ms O'Connor's son Jasper Lees began transitioning from female to male about two years ago, at the age of 18.

He's been part of a group of advocates leading the charge to remove discrimination against transgender and gender diverse people from the state's laws.

"Shortly after that, I started hormone replacement therapy which is a very slow process. I am now about two years down the track on that," Mr Lees said.

"I still can't grow a beard, so that is going well," he laughs.

On Tuesday night, Tasmania's Lower House of Parliament passed historic laws that would give parents the right to choose whether their child's gender is recorded on birth certificates, and remove the requirement for people to have sexual reassignment surgery to change their legal document.

Mr Lees commended Speaker Sue Hickey, who crossed the floor to pass the reforms, in spite of her Liberal colleagues.

"It was very gutsy of Madam Speaker," he said.

The inability to change his gender on his birth certificate was an issue Mr Lees had firsthand experience of.

Despite having also had chest reconstruction surgery, Jasper Lees was still not able to able to change his birth certificate because the operation is not classed as sexual reassignment surgery.

"It is highly confusing for people to say 'I am female' because I am, very obviously, not."

Mr Lees said transgender and gender diverse people should not have to have risky and expensive surgery to change gender.

"Requiring someone to remove their uterus or reproductive organs when they actually don't need to is sterilisation."

Cassy O'Connor has urged people "worried about this to empathise". ( ABC News: David Hudspeth )

As well as removing the barrier of surgery to officially change genders, Tasmanians would have the option to exclude gender from their birth certificate altogether, should the legislation pass the Upper House.

Mr Lees said the option not to list a gender was important for a lot of transgender, intersex and gender diverse people. For him, the choice would be to list his new gender.

"For me, I think I will, because my identity as a man is quite important to me," he said.

And how would it feel to hold his new birth certificate in his hands?

"I don't like the term like a new person, but yeah — like a new person."

"I will be able to be recognised as Jasper the man, which has up until this point has been very difficult, impossible really."

Ms O'Connor said the Greens' decision to pursue the changes to the Births Act was not based on her son alone.

"We knew that these law changes would make an enormous difference, not just to our children's lives but to the lives of other transgender and intersex people and that's really important. That's why we're here.

"We're in Parliament to do the right thing."

Law changes not guaranteed

To quash the changes, the Liberals need to persuade five Upper House independents to knock back the Labor-Greens amendments next week.

Most Legislative Councillors are waiting to be briefed before deciding, but some have indicated they will support it. The other possibility is that MLCs could push the issue to a committee, meaning the issue would drag into next year.

Ms O'Connor is hopeful the laws will pass the Upper House.

"It is going to make a big difference to peoples lives. We know transgender and intersex people are at risk of self-harm and suicide," she said.

"That alone should drive us to do the right thing."

This morning on local radio, Ms Hickey decried the lack of information about the changes.

"This has been around since January and there are lots of people who've tried to get information out of the Government," she said.

"There are lots of people saying 'urgh, we're going to have genderless birth certificates', but it's just about giving parents a choice.

"You don't have to have male or female on your passport, you don't have to have it on your driver's license, but it makes it easier later in life when a transgender person wants to cross over.

"Ninety-eight per cent per cent of Tasmanians will not be affected by this legislation at all, but for those who are transgender, it'll make the world of difference to them and their families."

For those who feel threatened by the changes, Mr Lees has this message.

"The decision for someone to transition isn't one that's taken lightly. It's never one that someone just makes on a snap decision, you don't just change gender," he said.

"It's not going to affect anyone but the trans community and people who love them."

Ms O'Connor said law reform would save lives; "I am certain of it."

"I think if we can encourage people who are worried about this to empathise and think about the people they love, hopefully we can overcome some of those fears."