A move to significantly toughen Western Australia's dangerous sex offender laws could be overturned by the High Court, the State Government says.

The Opposition has seized on the conditional release of convicted rapist Dennis John Lyddieth from prison to demand the Government deliver promised amendments to the laws.

The Government drafted legislation based on an urgent review it conducted last year, but has repeatedly said the existing Act is working as intended.

Attorney-General Michael Mischin accused the Opposition of scaremongering.

"I'm satisfied that the legislation is working as the Labor Party intended it work, back in 2006 when it passed," Mr Mischin said.

"It is nonsense to say otherwise. That particular criteria (for the release of prisoners) has not been changed since.

"They're being very opportunistic and either being very malicious or foolish, because this is working the way it was meant to work when they passed it."

Labor is demanding the Government bring on debate about amendments to the Act, saying the release of a convicted rapist shows the laws need to be toughened.

Lyddieth, who committed a dozen rapes before being imprisoned almost a quarter of a century ago, has been granted conditional release from jail.

Labor rejects claim changes could be unconstitutional

Shadow Attorney-General John Quigley would not reveal Labor's proposed changes, but rejected the Government's warning that tougher laws could be unconstitutional.

"Mark this spot with chalk. And I'll be back here to tell you what our amendments are. And they will not disappoint Perth," he said.

"And they will not disappoint the women of Western Australia. Or the citizens of Western Australia and they will be constitutional."

But Corrective Services Minister Joe Francis said the scope for change was limited and legislation that attempted to lock offenders up forever was unlikely to succeed.

"The advice I have is that if you start tinkering with laws and holding people in jail indefinitely, then there's a very real chance that amendments to the Sex Offenders Act will be struck down as unconstitutional by the High Court. It's a very real chance," Mr Francis said.

Police Minister Liza Harvey said she understood that people in Tuart Hill, where Lyddieth was released, would be appalled and anxious about his presence.

But she tried to reassure residents he would be closely watched.

"While he's been released into the community, he does have 44 conditions on his supervision order," she said.

Mrs Harvey said that previously, offenders have struggled to comply with their conditions and quickly ended up in detention.

"If he steps over the line on even one of those conditions, he will be back before the courts in no time flat," said Mrs Harvey said.

People living in the area will be able to view his photograph on the State Government's Community Protection website.