Premier Ben Carroll is expected to introduce the Independent Broad-based Anti-Corruption Commission (IBAC) Amendment Bill 2026 to the Victorian Parliament on Tuesday.
Once passed, the new laws will come into effect immediately.
The opposition and Greens say a late amendment to the bill, delivered at 6pm on Monday, would prevent the commission from investigating corruption in government-funded construction projects.
Under the changes, matters already addressed by the commission are off limits.
That includes organised-crime allegations referred to IBAC over two years ago by former premier Jacinta Allan relating to Big Build, which has completed more that 130 train and road infrastructure since 2015.
Before standing down as leader, Ms Allan in June announced IBAC would have its powers expanded, including follow-the-money powers.
Mr Carroll, who became Victorian premier in July, first announced his government would fast-track changes to expand IBAC's jurisdiction in August.
At the time he said legislation was being drafted to give IBAC follow-the-money powers and expand the definition of corrupt conduct.
Opposition Leader Jess Wilson accused Mr Carroll and his party of protecting his predecessors and vowed to fight the move in parliament.
"This government is not serious about getting to the bottom of the largest corruption scandal in this state's history, and it goes to the very core of the issue here: that Labor and the CFMEU are one in the same,'' Ms Wilson told reporters.
"They are not committed to ensuring that we understand how $15 billion of taxpayer money was siphoned off these sites into the pockets of criminals."
Victorian Greens leader Ellen Sandell also criticised the rushed process, revealing her party was only given the bill at 6pm on Monday night.
''It seems very fishy to be honest,'' Ms Sandell told ABC 774 Mornings.
''We actually need an anti-corruption watchdog that's up to scratch that can look into a wide range of measures that is fit for modern times.''
On Tuesday, Mr Carroll said investigations could be retrospective as long as there was a new referral or new information available, but would not say whether he would make a fresh referral.
He pointed to the upcoming royal commission into construction industry corruption, stating its scope rendered a new referral unnecessary.
"These are the biggest reforms to integrity in Victoria in a generation,'' Mr Carroll told reporters.
The state government is also set to introduce its controversial work-from-home laws this week.
Mr Carroll denied claims he had not listened to industry and business groups vehemently opposed to the new laws.
He emphasised the importance of working from home for productivity and participation, particularly for women and people with disabilities.
