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.
"It was a danger to passengers and other road users," union spokesman Rudd Hughes said.
There are also complaints about a lack of bathroom and cooking facilities, with drivers saying the bathrooms that do exist are unhygenic.
Hughes said that the union has repeatedly made requests with Go Bus to meet.
"We are very concerned about the conditions these drivers have described. We are told there is extremely inadequate and unhygienic bathroom facilities and no cooking facilities at the depot where drivers have their break. We understand that drivers are also being asked to have their breaks in their buses - on the road. It's not good enough," he said.
Hughes said one driver on a class 2 licence was told to drive a class 4 bus by the company and was forced to resign when he felt his safety would be at risk.
The bus company rejects claims of the resignations and concerns.
A spokesman said they were only aware of a single person quitting.
"We reject any suggestion that safety is being compromised or that the facilities we are providing are inadequate," he said.
"There will always be those who stand on the side lines hoping things will go wrong, but we work in the real world, which is appreciated by most people."
Go Bus said the facilities at the new Mangere Depot are "some of the best in the country."