Transport officials have ordered two Uber drivers off the road and warned others about breaking the law. They've also issued hundreds of warning letters to drivers thinking of working for Uber while other complaints about the app-based operation are under investigation.
Last month, Uber slashed the cost to become a driver and announced it was now a "ride-share" operation, so its drivers didn't need professional licences.
In response, the New Zealand Transport Agency has sent 296 letters to people considering driving for Uber, reminding them of the penalties for operating passengers services without a special endorsement on their licence and certificate of fitness for vehicles.
Conducting an unlicensed service could see them slapped with a $10,000 fine in court.
When Uber set up in New Zealand, it initially required its drivers to comply with most of the passenger service regulations, including having the endorsed licence and vehicle certificate.
Unlike taxis, however, its cars didn't use meters for fares, and the Taxi Federation says this makes it an illegal operation.
An NZTA spokesman said allowing drivers to operate a passenger service without the correct licence endorsement and vehicle certificate was illegal, which had been made clear to Uber.
The spokesman said Uber's checks on driver licences before allowing people on the road were less rigorous than the "mandatory background checks and the examination of a range of other risk factors which are carried out by the transport agency" before a passenger-endorsed licence is issued.