Bus drivers are yet again set to take strike in Auckland tomorrow.
About 60 drivers, who work for Pavlovich, will be picketing outside their workplace in the morning.
Pavlovich chief executive Bernard Pavlovich said he was not informed of the reason for the strike, but assumed it was related to a pay dispute.
First Union said disputes over driver pay and work conditions were heating up with a handful of companies.
Mr Pavlovich said he was only given 24 hours' notice of the strike and that this was inappropriate.
"What we do know is since November last year, we've met with the union representatives twice and obviously the key topic in most union discussions is pay rates so presumably that is the reason they are striking," he said.
"Resolution is in the hands of the union, they have an offer in front of them so it's up to them when they want to accept that offer.
"I think it's obvious to most lay people, and certainly those tuned in to industrial relations, that the union movement has wind in their sails. It's unfortunate the union is using their political wind to negatively impact on the service profession for the travelling public in Auckland."
First Union organiser Graham McKean said Pavolich was one of the lowest paying employers in the industry.
"There's a reason they have a lot of work, they pay bottom dollar. They're dragging the whole industry down," Mr McKean said.
"Many of these employees have been driving for decades and they have the responsibility of the well-being of hundreds of people a day on their shoulders. Pay them what they're worth," he said.
Auckland Transport said the strike action was not expected to cause major disruptions to tomorrow morning's services. Affected services will be listed on the Auckland Transport website.