A man who killed his dog and then roasted it in his backyard needs to be educated rather than put before the courts, says Auckland City's animal-loving mayor, John Banks.

Paea Taufa was found cooking his pitbull terrier-cross in an umu pit at his Mangere home in February.

Having struck the dog - rendering it unconscious - before killing it, Mr Taufa was not found to have done anything illegal and could not be prosecuted.

But Mr Banks, an animal rights activist for years, says better education on local customs and sensibilities is needed rather than changing the law.

"This activity is deeply offensive and totally wrong in our New Zealand society. For many people, this is absolutely repulsive," the mayor said.

"But the way forward is education. This man has obviously not been taught that killing and eating a domestic pet is not right in New Zealand."

In Tonga, where Mr Taufa is from, dog meat is considered a delicacy.

Mr Taufa said he was unaware that cooking his pet was not normal in New Zealand.

"I didn't know I couldn't cook the dog," he said. "In Tonga, any time there I cook the dog and it is okay. Dog is good food."

Animal welfare group Save Animals From Exploitation said it was totally opposed to killing and eating domestic pets.

Campaign director Hans Kriek said killing the dog was "horrific" but people criticising Mr Taufa were not completely innocent themselves.

"We are opposed of this, very much. But to a certain amount there is a lot of hypocrisy," Mr Kriek said.

"People will be quick to demonise this man and yet [New Zealand] is sending packs of horse meat every year to Europe, where they eat horse."

Mayor Banks said hating Mr Taufa for what he had done was uncalled for, as the level of cruelty and violence towards domestic pets was "shameful" in New Zealand.

The SPCA said it could not prosecute Mr Taufa because he had killed the dog in a humane way, with minimal pain and suffering.