The new laws, introduced today, are part of a $390-million pledge to overhaul the handling of the state's most serious criminals who post an unacceptable risk of offending again after jail release.

Under new emergency detention orders, offenders on supervision orders can be kept in jail up to seven days if they pose an imminent risk of committing serious sexual or violent acts.

This will apply even if they haven't breached a condition of their order.

Offenders will be housed at the $32 million-plus new secure facility being built at Ararat, which will provide treatment and interventions for up to 20 supervision order offenders.

The facility is due to open later this year after being announced last February.

Late last year, Wimmera Superintendent Paul Margetts, who was at the ward’s construction announcement, said Ararat police were prepared.

The scheme already applies to serious sex offenders, and allows courts to order the continued detention of an offender, or impose supervision including electronic monitoring, curfews and exclusion zones.

Offenders subject to post-sentence orders will be overseen by the recently established Post-Sentence Authority, chaired by former chief magistrate and state coroner, Judge Ian Gray.

Its creation was among recommendations from a review of supervision of serious criminals following the 2015 stabbing murder of teenager Masa Vukotic.

"We promised we would do everything we could to fix the system and that's exactly what we're doing - expanding the post-sentence scheme will help keep Victoria safe," Corrections Minister Gayle Tierney said.

- With Australian Associated Press