Half the 7375 dogs impounded in Auckland were destroyed in 2013-14 after being unclaimed by their owners and deemed unsuitable for adoption.
Only 508 dogs from the city's shelters were found new permanent homes.
"The 3016 dogs euthanised is way too high," said dog welfare advocate and Auckland Council member Dr Cathy Casey, commenting on the council's animal management report.
She said 151 or 5 per cent of the dogs put down could and should have been found new homes.
"Auckland Council must do better - every single adoptable dog must be given a second chance."