Under the new restrictions, Uber drivers must have held a NZ licence for two or more years, use a car no older than 2006, have their criminal and driving record checked and hold third party insurance.
But the New Zealand Transport Agency did not accept that Uber was operating a ride-share service and said anyone found to be transporting a passenger for payment without the proper passenger endorsement licence would be at risk of a $500 fine.
The agency's group manager for access and use Celia Patrick said Uber's new driver requirements were illegal.
"They are not operating within regulations ... and we will issue warnings or infringements and can take people to court."
She knew of one driver who had already been penalised by police.
Mrs Patrick said the specific licences were in place for safety reasons and the new Uber background checks were "far less rigorous than the mandatory background checks, medical checks and examination of a range of other risk factors which are carried out by the Transport Agency".
She urged anyone using Uber to ask to see the driver's passenger endorsement and if they can't produce one, take down their registration details and report them to the Transport Agency so they can investigate.
A spokesman for more than 800 Uber drivers also said the changes to the regulations were "totally illegal" and put passengers at risk.
"You won't know who you're getting in the car with and whether they're safe to be on the road."
The man did not want to be named out of fear Uber would kick him off the app for speaking out against it.
He worried the new requirements meant qualified, professional drivers would be replaced by "cowboys" keen to make some easy money.
Mr Kitschke said the fares were dropped to attract more customers so drivers would have "more bums on seats" and earn more fares.
Uber
• Has more than 1800 drivers in New Zealand
• Operates in 414 cities around the world
• Offers a service where someone can request a ride, a driver will accept them as a passenger, the ride can be tracked then payment is automatically deducted from the passenger's bank account.