The Post Primary Teachers Association has filed a class action against Acting Secretary for Education Peter Hughes over the Novopay fiasco.
The union signalled in February that it would take legal action on behalf of many of its 18,000 members who had been unpaid or underpaid as a result of the flawed payroll system.
The action, filed in the High Court at Wellington today, is against Mr Hughes because the union argues he has failed in his statutory duty to pay teachers.
The PPTA will be represented by Michael Reed QC and Paul Morten, who represented David Bain and recently won a damages case for Sir Bob Jones.
President Angela Roberts said it was a union's core business to fight for members' pay.