More than 350 dog owners have accidentally been sent other people's personal details by the Waikato District Council.
The Waikato District Council blamed the privacy breach on a printing error while it was processing dog registrations.
Dog owners who received the wrong personal details said they had been told by the council to shred the papers.
Tereza Pitt said she received a letter with her details on the front, and another person's name, address, date of birth, phone numbers and details about their dog on the back.
"Somebody out there has got all my details just like I've got somebody else's details," she said.