A new high-security youth justice centre will be built by the state government in Werribee South following a string of violent uprisings, escapes and several damning reviews of existing facilities at Malmsbury and Parkville.

The Andrews government is expected to announce the 250-bed youth detention centre within weeks in a desperate bid to staunch the crisis that has plagued Victoria's youth justice system and threatens the government's re-election prospects.

According to a senior government source, the project will cost about $250million and is understood to have been commissioned by the Department of Health and Human Services more than six months ago, after repeated warnings about overcrowding at Malmsbury and Parkville.

The youth justice centre will include a high-security unit for the state's worst youth offenders. It will be built on a greenfield site in Werribee South, off the Princes Freeway, but the location is expected to cause ructions with residents in the growth corridor south-west of Melbourne.