About 70 Ritchies Murphy bus drivers in Auckland are striking this morning over work and pay conditions.
Auckland Transport on its website said more than 80 services in South Auckland between 6am and 9.30am have been cancelled.
This follows similar protests from members at Go Bus and Pavlovich Coachlines depots.
First Union, which represented the workers, said drivers at Ritchies Murphy have unacceptable employment conditions.
No-one from Ritchies Murphy was immediately available to comment.
Ritchies Murphy Transport is an affiliate company of Ritchies Transport who has previously requested to bring in 200 migrant workers due to claims there was a worker shortage, a statement from First Union reads.
Auckland Transport has released a full list of the affected AT Metro bus services.