Reports say Victoria's corruption commission has questioned Premier Daniel Andrews over issues including branch stacking and misuse of public resources.

According to The Age, Mr Andrews has been grilled by Victoria's Independent Broad-based Anti-Corruption Commission (IBAC) in an investigation that has already found issues with the Labor Party’s culture, including claims that it encouraged the serious misuse of public resources.

IBAC has reportedly concluded in a draft document that cultural failings were systemic within Victorian Labor, and questioned whether reforms adopted by the ALP will stop branch stacking and other misconduct.

Mr Andrews allegedly conceded to IBAC that branch stacking, rule breaking, and a failure to to allow whistleblowers to raise complaints is not likely to be limited to the state branch’s moderate faction. 

“The evidence adduced enables the conclusion that these practices have been approved or condoned by party leadership for decades,” IBAC concluded, according to reports.

“These unethical practices were embedded within the Branch and are systemic to all of the factions.

“Leaders must be prepared to expose and denounce such activity regardless of their alignment. Without the rigorous participation of the leaders of the branch, the reforms proposed in this report are unlikely to be effective.”

Mr Andrews has refused to confirm whether he was questioned or to comment on the report.

“This is real, it is detailed, it's happening, it's not yet finished. When it is finished, we'll be able to talk about it,” he said.

“You can be at somewhat of a disadvantage when you're not prepared to trample all over processes, sometimes that means you're not in a position to refute things that are plainly wrong.”

The Victorian Opposition has called on the Premier to resign.