Sunglass Hut underpaid hundreds of its part-time workers by about $2.3m over more than five years, but has avoided prosecution after entering a court-enforceable undertaking to repay the cash and agreeing to a $50,000 “contrition” payment.

Between 2010 and 2016, Luxottica Retail Australia Pty Ltd, trading as Sunglass Hut, failed to reach an agreement with part-time workers as required by the general retail industry award.

As a result, the company failed to pay $2,294,496 in overtime rates for work performed outside regular hours, to 620 employees at 253 stores across the country.

The fair work ombudsman, Sandra Parker, said the undertaking was appropriate as the company had committed to overhauling workplace practices and rectifying all underpayments.

“Sunglass Hut breached workplace laws and their conduct falls short of lawful obligations to their employees, and community expectations,” Parker said.

Sunglass Hut has already back paid $1,485,590 to 457 staff, with $815,391 outstanding.

As a gesture of contrition, Sunglass Hut must also hand over $50,000 to the National Association of Community Legal Centres.

“This matter highlights that if employers incorrectly apply award conditions, it can have extensive and expensive consequences across the business for years to come,” Parker said in a statement.

“This outcome should also serve as a warning to all businesses that they need to actively check that they are paying their staff correctly.”

Sunglass Hut must call in external auditors to check pay and conditions for workers every year until the undertaking ends in 2022.

Luxottica must also issue a letter of apology to each of the affected workers.

The company has been contacted for comment.