Conflicting reports have emerged of Go Bus drivers resigning on the first day of the company's new Auckland routes because of safety concerns.
First Union, which represents drivers, says up to nine drivers have quit in the past week.
Go Bus, however, is denying the claims.
NZ Bus lost its southern services to Wellington bus company Go Bus earlier this year.
Drivers have complained about a lack of induction training, with one driver saying he was sent out in a bus he had never driven before.