Sadists who hacked off an eight-week-old puppy's ears with a pair of scissors have avoided prosecution because witnesses refused to give evidence in court.

The puppy, which has been nicknamed Trooper, was brought into the SPCA by a person who found it wandering around the Gate Pa Shopping Centre in Tauranga in November.

Its ears had been crudely chopped off in a "disgusting" act of animal cruelty which left it in an enormous amount of pain, SPCA inspector Jason Blair said.

After a lengthy investigation, Mr Blair established where the puppy came from and managed to find out what happened from several residents, but they refused to go on the record with their evidence, despite the SPCA's numerous attempts to persuade them to.

"They spoke to me but they were quite clear in their minds that they wanted to remain anonymous because of fear of the people that were involved," he told NZPA.

"It's frustrating knowing who's responsible but not being able to take that extra step to follow through, which is a common problem that the SPCA has because the animals don't talk so we do rely on either a confession or witness statements."

However, Mr Blair said that a 27-year-old man had been charged for failing to get veterinary treatment to alleviate the puppy's pain and suffering, which carries a maximum penalty of 12 months imprisonment and or a $50,000 fine.

He will appear in Tauranga District Court on July 18.

The case caused a public outcry and a reward was offered for information which led to a prosecution.

- NZPA