Mr Stewart, a police officer, said he was walking Thor and Gisa back to his car when they were confronted by a pack of around "eight" pig dogs as they rounded a bend and the dogs suddenly began fighting Thor.
Masterton District Council has told the Times-Age staff are investigating the attack but officers have been told only four dogs were involved.
Dogs were a pack animal and this pack took an "instant dislike" to Thor, Mr Stewart said.
"There were at least seven dogs. They just latched on to Thor."
He grabbed Thor by the collar, but the dogs kept attacking and Mr Stewart got thrown to the ground landing on top of Thor while the other dog Gisa just stood back watching the attack. "It was a pack frenzy," he said.
Four dogs latched on to Thor, biting and ripping a chunk off his ear, causing internal injuries and injuries to his head, all four legs and chest - Mr Stewart was also bitten in several places.
Mr Stewart said the pig dogs' owner couldn't control them.
" He'd pull one off and the others would jump in and keep going."
It was a frightening few minutes, he said.
"There were at least four of them attacking while another four or so circled us," he said.
The owner of the pig dogs ran back to his bike and grabbed a chain which he hit the dogs with to get them off Mr Stewart and his dog.
Thor was rushed to a vet clinic and into surgery and may now have a permanent limp.
Ms Wolterbeek said Thor was depressed.
"He just isn't himself any more."
The couple made a formal complaint to Masterton District Council and while staff have contacted Ms Wolterbeek, Mr Stewart is still waiting to speak with someone.
He said he had heard of other incidents involving the same pack of dogs and people were now too afraid to walk the paper road with their dogs, fearing they, too, will be attacked.
Mr Stewart has spoken to other people who were on the road around the same time, including a doctor, who saw the pack of dogs and can attest to how many dogs were involved.
Masterton District Council's chief executive Wes ten Hove said staff were investigating the incident but there were "clearly two very different sides to this story".
Any investigation had to take into account all the circumstances before the council determined the appropriate course of action, he said.