A Wellington vet says he is concerned about faults in some microchips used to identify dogs.
Microchipping enables the easy identification of lost or stolen dogs. It can cost up to $80 per animal and is required by law.
A senior vet at the Miramar Vet Hospital says that over the past couple of years, he has noticed chips failing to scan.
Allan Probert is worried that people are living with a false sense of security about the microchip's ability to track and find their pet if it goes missing.
"My concern - and I think it's probably every vet's worst nightmare - would be that a dog or a cat might be inadvertently euthanised, even though it's microchipped."
Mr Probert says the problem is occurring across a range of chip makers and his clinic is now scanning every dog that comes in to make sure they are working.