Ritchies Coachlines is defending its bid to bring in 110 drivers from overseas.
The move needs the approval of Immigration New Zealand and the company must first prove the workers are not available locally.
Auckland Transport awarded Ritchies Coachlines the contract to run buses on the North Shore from September.
But the company said so far it had not been able to find enough drivers locally and had asked Immigration New Zealand if it could bring in 110 of them from overseas to plug the gap.
But the drivers' union said the only reason Ritchies won the contract was because it was willing to undercut the wages offered by other companies and allowing it to employ foreign drivers would start a race to the bottom on wages across the sector.
Ritchies spokesman Matthew Todd said his company had been working hard with Work and Income to find enough locals willing to take up jobs on its newly-acquired North Shore run, but after a month of trying had only managed to find 15 new drivers.
This was despite offering them six to eight weeks paid training.
"It's very difficult to get people in to the buses. We have a lot of people who have the relevant licences. We get tripped up a lot when it comes to criminal history checks. It's unfortunate to say but passing drug tests as well [is a challenge for] some of the people who come in. Driving a bus, you need to be a fit and proper person."
Mr Todd said the company would continue trying to recruit locally but only had until late June before it would need to look overseas for drivers including in Fiji, Samoa and the Philippines.
He admitted the $20.20 an hour it paid drivers would be difficult to get by on in Auckland but said this was the budget it had to work with.
"Lets face it, any job in the world, if you pay enough, you'll get people to do it but...those costs will have to be passed on."
One of the factors limiting what they could pay was the amount Auckland Transport was willing to pay for Ritchies to provide public transport on the North Shore.
"It does sound like a very simple thing of you know just pay some people more and it will go away. I think the issue's much deeper and more complicated than that and I think it needs to be discussed between transport operators, the unions and local councils."
'Auckland Transport is the villain here' - First Union
But First Union's Graham McKean urged Immigration New Zealand to turn down Ritchies' request to head overseas for drivers.
He said there was no shortage of drivers and the move was more about driving down wages.
"The problem with Ritchies is that they pay over a dollar an hour less than the industry so their retention rates are minimal. People get trained up then they'll go to other bus companies where the rates are better. Again Ritchies brings it upon themselves.
"If they paid market rates, it would be a different conversation."
Mr McKean said Ritchies won the North Shore contract from Auckland Transport by undercutting its competitors with a low ball bid made possible by its willingness to pay low wages.
"Auckland Transport is the villain here. Auckland Transport is effectively rewarding low paying companies by giving them a greater share of the market. And what that does is it creates a gravitational pull and drags down the terms and conditions of all the other bus drivers."
Auckland Transport declined a request for an interview noting it was the bus companies that bid for contracts that set wages and conditions, not the council.
Immigration New Zealand said it would consult with groups including unions before it decided on whether Ritchies should be allowed to employ overseas workers but said it would first have to be established the workers were not able to be found locally.
Transport Minister Phil Twyford was reviewing the way public transport was funded to see if that was having an impact on employment conditions.