Western Australia is a step closer to legalising voluntary euthanasia for terminally ill adults, with the State Government's assisted dying laws easily passing their first hurdle.

Key points: The Lower House was widely expected to support the Government's VAD laws

The Lower House was widely expected to support the Government's VAD laws The vote in the Upper House of the WA Parliament is expected to be much tighter

The vote in the Upper House of the WA Parliament is expected to be much tighter Hundreds of supporters rallied at State Parliament in support of the bill

The Lower House of WA's Parliament overwhelmingly backed the Government's voluntary assisted dying (VAD) laws on Tuesday night, with the first vote on the legislation coming in at 44 votes in favour to 12 against.

But that vote was just the first of several potential obstacles the Government must overcome for WA to legalise VAD, with much bigger hurdles still to come — including what is expected to be an extremely tight vote in the Upper House.

That first vote came as supporters again urged MPs to back voluntary euthanasia, with several hundred rallying at State Parliament in support of the bill, ahead of the Legislative Assembly's decision.

If the Upper House approves the legislation when it goes to a final vote later this year, WA would become the second Australian state to legalise VAD, after Victoria.

The proposed bill would give terminally ill WA adults who are likely to die within six months the right to access medical help to end their own life.

Several of the bill's critics outlined their objections to it ahead of the vote, with concerns including the adequacy of safeguards in the Government's proposal, and the lack of a requirement for a psychiatric assessment.

'No-one can tell me doctors don't make mistakes'

Police Minister Michelle Roberts is the highest-profile MP to confirm her opposition to the bill, raising concerns about WA's safeguards being less stringent than those in place in Victoria.

"The fact that we need safeguards means there is something inherently worrying about the principle," Ms Roberts said.

Michelle Roberts is the highest-profile MP to speak against VAD laws. ( ABC News: James Carmody )

"There exists the very real [opportunity] for abuse."

Ms Roberts warned the legislation could have "tragic consequences" and cause some people to have their lives "cut short" unnecessarily.

She also pointed to the case of former Labor MP Batong Pham, who recovered from a stroke which doctors did not expect him to survive.

"No-one can tell me doctors don't make mistakes," she said.

Health Minister Roger Cook has repeatedly described the legislation as "cautious and safe", with the Government arguing the overwhelming majority of West Australians want to see VAD legalised.

He dismissed criticism from some MPs that WA's bill was less safe than the Victorian law, saying that was "just not true".

"This bill will protect vulnerable people in ways that do not exist now," he said.

"This is a watershed moment. We must have the courage and confidence to uphold these freedoms for the most vulnerable in our society."

Several MPs made tearful speeches during the first stage of debate, with Liberal leader Liza Harvey and Nationals Leader Mia Davies among those to get emotional.

"If I was faced with a diagnosis of lung cancer tomorrow, I would want the option of voluntary assisted dying," Ms Davies, a supporter of the bill, said.

'This legislation cannot be allowed'

One day after the vote, several hundred people rallied outside Parliament against the proposed laws.

Some carried placards saying "Kill Pain Not Patients", "Doctors Should Save Lives, Not Take Lives" and "Care Not Killing".

Among those watching from the sidelines was Ms Roberts, along with Liberal MPs Nick Goiran and Alyssa Hayden.

Tennis great Margaret Court held up a banner behind the speakers.

Hundreds of people gathered to make their opposition to the proposed laws known. ( ABC News: Nicolas Perptich )

Protesters called for the Government to dump the voluntary assisted dying plans. ( ABC News: Hugh Sando )

Nurse practitioner Lou Angus told the crowd dying people were not a burden, and end-of-life care should be properly funded to look after them.

She said the proposed bill had weak safeguards and would end in wrongful deaths.

"This legislation cannot be allowed," she said.

Peter Abetz, from the Australian Christian Lobby, was concerned terminally ill people might feel they had no choice but to end their own lives.

"The very fact of its availability actually creates a subtle pressure to use it, because when you are terminally ill, you can't escape the fact that you area burden to your family. That's the reality," he said.

Earlier, Premier Mark McGowan said Parliament had reflected the overwhelming support of the public for voluntary assisted dying.

Opponents of the proposed laws believe more money should be spent on end-of-life care. ( ABC News: Hugh Sando )

He urged MPs to not unnecessarily delay the legislation as it continued to be examined in detail in the Legislative Assembly.

"The overwhelming feedback from the public is they'd like to see these laws passed, and I'd urge all MPs to take account of that," Mr McGowan said.

"I think it's incumbent on us to listen to the community, and this is a prime example of that."

Community support 'reaches point of no return'

The VAD supporters who gathered outside Parliament on Tuesday included Belinda Teh, whose mother died from breast cancer.

She told the gathering the moment they had all been waiting for had arrived.

"I have been warned by countless people who have been campaigning for a long, long time that success is not guaranteed and that we could lose by one vote in the Upper House," she said.

Hundreds of VAD supporters gathered outside Parliament House. ( ABC News: Hugh Sando )

The mood among supporters of voluntary euthanasia was positive ahead of the vote. ( ABC News: Hugh Sando )

"And even though I don't want to believe it I know that they are right. It is entirely possible that our Parliament could fail to pass this bill.

"And yet I have hope for a future where a dying person who is suffering and in agony will be able to ask, 'can you help me', without shame, without fear and without judgement."

"Community support for voluntary assisted dying has reached the point of no return."

Lizz Clarke — an experienced nurse whose husband Colin is terminally ill and sent a video to MPs in support of VAD — also addressed the crowd.

She said she had witnessed both good and bad deaths.

"Bad deaths are torment and pain, loss of control, loss of dignity, loss of self. Bad deaths hold relief just out of reach, keeping that person in limbo," she said.

Supporters of VAD laws were warned that ultimately Parliament could reject the bill. ( ABC News: Hugh Sando )

The Government argues the vast majority of West Australians support voluntary euthanasia. ( ABC News: Hugh Sando )

"We can protect their [the terminally ill] autonomy, give them back some control of their lives."