The Ministry for Primary Industries (MPI) has uncovered a "black-market butchery" operation in Waikato, which has been selling sheep, cow and goat meat for several years.
Officers recently seized 22 freshly processed sheep from an Atiamuri farm that were destined for sale, and several thousand dollars.
The ministry said the operator was likely to be prosecuted, and could face five years in prison or a fine of up to $100,000.
MPI spokesperson Brendon Mikkelsen said members of the public should source their meat from regulated outlets like butcheries, supermarkets and other legitimate meat suppliers.
"This is particularly the case in the lead-up to Christmas where illegal meat operations are, traditionally, more prevalent.
"We are appealing to the public to report any suspicious or unlicensed meat suppliers. If we receive information about these kinds of operations, we will shut them down, and prosecute those involved in making money from selling potentially substandard product."
Another large-scale illegal home kill operation was uncovered in Auckland last week.