Australia’s largest speciality fashion retailer has copped a $29,000 fine for underpaying its workers long service leave entitlements.

Mosaic Brands, which has 1100 stores, including brands Millers, Rivers, Katies, Rockmans and Noni B, pleaded guilty to 324 offences in Downing Centre Local Court and was fined on May 19.

The NSW Employee Relations Inspectorate uncovered systemic underpayments of long service leave to 223 workers arising from payroll system errors.

The magistrate concluded the underpayments were not deliberate, but the offences were too serious and widespread for there to be no penalty imposed.

The case involved the largest ever number of offences prosecuted simultaneously in NSW for long service leave underpayments.

Industrial Relations Minister Sophie Cotsis said the record fine signalled a renewed focus on compliance to support an expansion of long service leave entitlements to tens of thousands of workers.

The Minns government has promised to expand long service leave through a portable leave scheme for gig, disability, home-care and other precarious workers.

“The NSW government is committed to standing up for workers and investigating businesses who are short-changing their staff, particularly at a time when so many individuals and family are doing it tough,” Ms Cotsis said in a statement on Tuesday.

She said the court’s ruling was a reminder to employers that they must ensure their employees receive their full entitlements.

“Long service leave applies to most NSW employees who are full-time, part-time or casuals,” Ms Cotsis said.

“It is up to the employer to conduct their own internal compliance reviews on a regular basis to make sure they are paying long service leave correctly.”

Mosaic has been contacted for comment.