Post-jail supervision of some of Victoria's worst sex criminals will be boosted from Wednesday in a move the state government hopes will prevent attacks by known predators.

But the government will not say how many offenders will be managed by the new "Post-Sentence Authority" – formed as part of the wide-ranging response to the murder of 17-year-old Masa Vukotic in 2015 – which officially begins its work today.

The government says the authority will oversee the management of offenders like Sean Christian Price, who stabbed Ms Vukotic in a park near her Doncaster home as she took an evening walk, making dangerous criminals less likely to strike again.

Price was under a supervision order when he killed the schoolgirl, and the murder, which shocked the state, was one of a series of brutal crimes committed by men who were on bail or under other official forms of management.

Corrections Minister Gayle Tierney said the authority will "provide independent oversight of the state’s post-sentence scheme, which allows for the ongoing detention and supervision of serious sex offenders who pose an unacceptable risk to the community after being released from prison".