Outlaw motorcycle gangs supplied drugs and prostitutes to construction workers at the Wonthaggi desalination plant, confidential Victorian cabinet documents reveal.
The documents say the Comancheros, Outcasts, Black Uhlans and Rebels motorcycle gangs used three rented Wonthaggi homes as a base for their narcotics and prostitution operations.
Bikies were also employed to drive construction management to and from work and to social functions.
The revelations were contained in a cabinet-in-confidence report written by the government's former Construction Code Compliance Unit officer, Nigel Hadgkiss.
The documents have never been made public but details from sections of the report were published in News Limited newspapers on Tuesday.
The report was commissioned in the wake of the 2012 dispute between construction units and building company Grocon.
It is alleged the Construction, Forestry, Mining and Energy Union (CFMEU) used bullying and standover tactics in the Grocon dispute and that the union had long been deliberately contemptuous of the law and would be willing to pay penalties to continue engaging in illegal activity.
The CFMEU was convicted on Monday in the Supreme Court of four counts of criminal and two of civil contempt for blocking access to Grocon sites including the Myer Emporium site in central Melbourne in August 2012 against court orders. It was fined $1.25 million.
Victorian Premier Denis Napthine said illegal activity on building sites must be stopped.
"There seems to be no doubt that there is an unholy alliance between some of the building construction unions and bikie gangs and the illegal activities. It is an absolutely unholy alliance and it must be stopped, it must be smashed," he told reporters.