Higher education workers were underpaid by at least $83 million over the last three years.
The University of Melbourne topped the list of institutions owing money to staff, underpaying workers by about $31.6 million according to analysis from the National Tertiary Education Union.
The University of Sydney came in second with about $12.7m owed to workers, followed by RMIT with $10m and Monash University with $8.6m.
The report showed higher education workers in Victoria were underpaid by about $50m in total, almost $25m in NSW and $2m in Queensland.
"Systemic wage theft has been baked into universities' business models," according to the union's national president Dr Alison Barnes.
The union says mass casualisation was behind underpayment issues and a greater number of workers need access to secure positions.
"The sheer scale of wage theft in higher education is staggering," Dr Barnes said.
"It's absolutely shameful that so many Australian university staff have had wages stolen."
The study looked at 34 incidents of underpayment at 22 universities.
It does not include ongoing cases relating to Monash, the University of NSW and Deakin University, leading the union to predict workers across the sector could be owed as much as $90 million.
Last year, the University of Melbourne apologised to about 15,000 current and former casual staff who were owed $22 million in back pay.
The union is now pushing for the Federal Labor government to criminalise wage theft and ensure employers face tough penalties if found guilty, and calling for a fresh probe into university governance.
