A Christchurch dairy has been fined for exploiting and underpaying a staff member who worked for 92 hours a week - for under the minimum wage.

Shirley dairy, Indy Supa, underpaid a worker by more than $103,000 over a four-year period.

The Employment Relations Authority has ordered it to pay $61,000, as well as ordering sole director Kavita Tailor and her spouse - Mayurkumar Tailor - to collectively pay $24,000

It's one of the highest amounts of money owed to a single worker investigated by the Labour Inspectorate in recent years.

It found the staff member often worked up to 92 hours per week, was not paid the minimum wage, or correct annual leave and holiday pay.