The survey, conducted by workplace watchdog the Fair Work Ombudsman, found that some workers were on cash-in-hand wages as low as $10 per hour, with Fair Work Ombudsman Natalie James laying blame at the door of major chains such as Woolworths, saying that it is no excuse to claim not being aware of the wages paid by contractors and sub-contractors.
"There were cases where the underpayment of workers was inevitable, with the insufficient money being paid by Woolworths for all the contractors to make a profit while meeting their employees' entitlements," said James.
"You see no evil when you hold your hands over your eyes."
However, a Woolworths spokeswoman reiterated the supermarket giant’s commitment to workplace law and co-operating with the Fair Work Ombudsman to ensure the fair and ethical treatment of trolley workers.
“Woolworths believes that if the FWO were to conduct an inquiry into trolley collection procurement practices as they exist today our arrangements would not be open to criticisms of the kind levelled in the FWO's report," said the spokeswoman.
“Since 2014 Woolworths has put in place significant additional governance arrangements to help ensure compliance by its trolley collection contractors with workplace laws.
"Woolworths takes all matters raised by the FWO seriously and has a zero-tolerance approach to all non-compliance with workplace law."
The release of the findings follows the latest alleged exploitation of cleaning staff and trolley workers in Tasmania and New South Wales, which came to light last week.
At the time the investigation was conducted, the minimum adult wage for trolley workers ranged between $18 and $22.50 per hour, depending on the nature of the position.
The Fair Work Ombudsman has called on Woolworths to do more to prevent the exploitation of trolley workers, who often struggle with English and are therefore vulnerable to coercion.
“We are recommending Woolworths enter into a compliance partnership with us to publicly demonstrate its commitment to stamping out the exploitation of vulnerable trolley collectors," the ombudsman said in a statement.
A 12-month investigation that audited 130 Woolworths supermarkets has found that trolley collectors at one in three stores nationwide are being illegally underpaid, 80 percent of sites are violating workplace laws and 50 percent had multiple legal breaches.