Steel and Tube has been fined a record $1.9 million for making false and misleading representations about its steel mesh products.
The company earlier pleaded guilty to 24 charges under the Fair Trading Act.
The charges related to claims that Steel and Tube made between 2012 and 2016 about the products being independently tested, when they were not.
The company also falsely said products met the Australia-New Zealand standard for reinforcing steel, but they had not been properly aged or tested.
In a sentencing judgment released today, Judge Cathcart said Steel and Tube acted in a "grossly negligent" way and senior management should have known about the large-scale non-compliance over the four-year period.
The fine is the highest ever handed down under the Fair Trading Act.