About 15,000 family pets need to have a new microchip inserted, amid fears their old ones won't work.
The news has left one pet owner outraged, and worried that it might lead to some domestic cats being mistaken for strays and put down.
Anne Batley Burton likes to keep her rescue cats close, but fears what could happen if they wander over the back fence.
"A very dangerous situation for pet owners and their animals, particularly cats," she said.
Ms Batley Burton says some of her cats are micro-chipped with a product called BioTec, manufactured by Virbac.
There have been problems with the brand and model in the past. In 2012, some pets needed new chips implanted, because their original ones couldn't be detected when scanned.
The affected owners had the chips replaced and vets stopped implanting them, and that was the end of the story.
But, on Wednesday, Newshub obtained an email sent by a Virbac employee on Monday, saying that all animals with an original BioTec-branded microchip now needed to have a new one inserted.
Why? The letter says: "Because it now seems possible all the BioTec chips might fail over time."
Two veterinary clinics, spoken to by Newshub on Wednesday, confirmed they received the letter from Virbac on Monday.
"These microchips were commonly used between 2009 and 2012, so lots of cats and dogs will have them," said vet Jessica Howes.
Up to 15,000 pets could be affected, the BioTec implants were inserted between 2009 and 2012 and no other Virbac products have been affected.
The New Zealand Veterinary Association says to contact your vet if the 15 digit number for your pet's microchip begins with 900088, 9000088, or 9000010.
It's concerns about the technology that have Ms Batley Burton worried.
"I mean it means that the technology is not that great," she said.
In some areas, councils are proposing to destroy cats that aren't micro-chipped or otherwise identifiable.
"It would be a very sad situation, if these poor cats were put down, purely because they have not had the luck of being micro-chipped and even if they were, who knows, looks like a lot of them are not going to work," she said.
Virbac product manager Simon Clark says that's unlikely.
"Councils do not give up on animals easily," he said. "They put an extraordinary amount of effort into trying to find those owners."
Virbac says concerned pet owners don't need to do anything - if their pets' chip need replacing, they'll be contacted by their vet.
And Virbac will foot the bill.
The SPCA also suggests that pet owners put a collar and identification tag on their cats and dogs, which will help if they stray too far from home.