The Fair Work Ombudsman has launched legal action against a national advertising company, alleging it underpaid 45 employees almost $60,000.

OHMedia Melbourne Pty Ltd and company director and part-owner Wen Zhou, also known as Joseph Chou, will face the Federal Magistrates Court in late March.

It's alleged OHMedia Melbourne underpaid 45 casual employees in Brisbane, Sydney, Melbourne and Adelaide a total of $59,145 between March and April, 2011.

The employees worked at stalls outside supermarkets promoting prepaid SIM cards and top-up vouchers supplied by global telco Lycamobile, an OHMedia Melbourne client.

Several of the employees were foreign nationals who were in Australia on student and working holiday visas.

It's alleged that more than $48,000 of the underpayment relates to 34 Brisbane-based employees - including seven juniors aged between 18 and 21 - who worked up to 133 hours without being paid.

Complaints by employees to the Fair Work Ombudsman prompted an investigation.

Fair Work Ombudsman Nicholas Wilson said the amount of the alleged underpayment and the vulnerability of the employees were key factors in the decision to prosecute.

"Foreign workers may not necessarily be aware of their full entitlements in the workplace and are therefore particularly vulnerable," he said in a statement.

The company could face penalties of up to $33,000 for each proved breach.

The Fair Work Ombudsman is seeking a court order for back-payments for the affected employees.

Comment was being sought from the company.