VICTORIA Police was last night searching for a convicted murderer who has breached parole at least three times since being released.

The search was under way as concerns grew around the parole board decision that saw serial rapist Adrian Ernest Bayley remain free to kill ABC employee Jill Meagher.

A manhunt is under way for Clive Edward Stone, 58, who was released on parole a year ago, 26 years after he was sentenced to life in prison for the murder and mutilation of intellectually disabled woman Lorna Jane Gibson.

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Police warned members of the public not to approach Stone, who is believed to still be in the Melbourne area.

He was initially released on parole in 2007, but was sent back to prison twice for breaching curfew and alcohol provisions.

The development came as the state's Sentencing Advisory Council head Arie Freiberg said the Victorian parole board had made a "catastrophic" error allowing Bayley to remain on parole when he committed a violent offence a year before he raped and killed Meagher. "There is a question of what discretion you want to leave with the board," Professor Freiberg.

Bayley was eight years into an 11-year sentence for 16 rapes when he was released in 2010.

He had previously served three years of a five-year sentence for attacking three women, including a 16-year-old whom he raped when he was 18.

Bayley, 41, will be sentenced next week for raping and murdering Meagher, whom he attacked last September as the 29-year-old Irishwoman walked home after drinks with friends in Brunswick.

He had remained on parole despite brutally attacking a man in Geelong in August 2011.

Professor Freiberg said data showed Bayley's more recent rape sentence had been at the higher end of comparable sentences. "The average total effective sentence for a small number of rapes and similar offences is in the range of about six years with a four-year, non-parole period," he said. "He got 11 (years), which is double the average.

"There are some jurisdictions which impose longer sentences. I don't know if they're more effective but it certainly would have kept him out of the community for a longer period of time, which is not to guarantee that he, at the conclusion of the sentence . . . wouldn't have reoffended."