A media company run by prominent broadcaster and businessman Craig Hutchison has been penalised for illegally exploiting young workers.

In a significant test of how interns can be treated under industrial law, Crocmedia faced court action after the workplace watchdog found the company had grossly underpaid two workers tens of thousands of dollars.

The Federal Circuit Court on Thursday handed down fines of $24,000 against the Melbourne-based media company, which develops and sells radio, TV and online content.

A probe by the Fair Work Ombudsman revealed serious underpayments of two young people who approached Crocmedia seeking work experience in the industry.

For between six months to a year, the workers produced radio programs for the SEN network and routinely worked multiple weekly shifts, including the "graveyard" shifts from midnight to 6am.