The workplace watchdog has found three-quarters of inspected Caltex petrol stations have legal breaches.
The Fair Work Ombudsman inspectors found evidence of underpayment of wages, non-payment of overtime and penalty rates as well as record keeping and pay slip breaches.
Inspectors visited 25 petrol stations run by 23 Caltex franchisees in Brisbane, Sydney, Melbourne and Adelaide.
Caltex said the sites inspected were not representative of the 1900 outlets across Australia.
“Since instances of wage underpayment in our franchise network first emerged in 2016, Caltex has been very clear – unlawful behaviour would not be tolerated and we will act decisively to remove the practice from our franchise network,” a company spokeswoman said.