Now a state MP, Mr Limbrick is determined 28 years later that Denyer remain locked up forever.

The Liberal Democrat has helped launch a petition calling for legislation that would keep Denyer behind bars.

Denyer is serving a minimum 30-year sentence for stabbing and strangling three young women in suburban Frankston in 1993.

Denyer, who now identifies as Paula, will become eligible for parole in mid-2023.

Mr Limbrick, Natalie's parents, Brian and Carmel and Natalie's friend Karen fronted the media on Monday to draw attention to their petition.

"What we are asking the government to do is make sure that Paul Denyer is locked up forever," Mr Limbrick said.

"I speak for all of us when we say we are concerned that if Denyer did finally get released one day, and we had the opportunity to try and prevent that and did nothing, how could we live with ourselves?"

Mr Limbrick met Natalie when she was in her last year of school and he had started university.

She was 17 when Denyer killed her.

Her family have no doubt that if Denyer is released, he will try to kill again.

Karen said what Denyer did still resonated in Frankston.

"There's not a woman who doesn't check her back seat before she gets in the car," she said.

"At the moment at least I know where he is."

Mr Limbrick said there were various ways the state government could legislate to keep Denyer in jail and he has spoken to Attorney-General Jaclyn Symes.

"All of us have lived for the last 28 years dreading the day that this would come. Now, we're approaching that day," he said.

Brian Russell said their whole family had suffered. When he needed surgery for bowel cancer, his doctor told him the trauma of what happened to his daughter probably triggered the illness.

"You learn to get out of the bed of a morning and put one foot in front of the other, but it's there in front of you all the time," he said.

"Probably the only thing that gave us any consolation was the fact he was locked up and couldn't do this to any other families.

"I'd hate anybody to go through that we went through."

He said their wish to keep Denyer in jail was not because they are vindictive, but because of their fear.

Denyer was originally sentenced to three life sentences, but it was reduced on appeal, a decision Mr Russell described as a kick in the guts.

Mr Limbrick said that given 2022 will be an election year, the government must act now or else it could be too late.

Opposition leader Michael O'Brien said he would back any legislation to keep Denyer in jail, no matter who brings it forward.

"Victoria will be a less safe place if that despicable murderer is on our streets again and I'll support legislation to keep him behind bars where he belongs," Mr O'Brien said.

Australian Associated Press