"She couldn't stand properly, the closest comparison I could make is she looked like she had Parkinson's disease and was shaking like a leaf."
The couple bundled the dog into the back of their car and took it to a vet.
"There we were told what we already knew - the dog was not going to last long and the only realistic option was to euthanise her."
The wife knelt on the floor with the dog, stroking her until she died.
"It was good to see her go, to see the shaking stop and to see the fear in her eyes go away - we definitely felt we had done the right thing."
The couple told the veterinary service they would pay for the appointment, but their offer was not taken up by Bay Vets who covered the cost.
The incident left the couple angry.
"It's unthinkable anyone could let a pet get to the stage this dog was in, it was just inhumane."
When police and council staff were called to Bay Vets to inspect the dog it was recognised by a council dog ranger.
Council community regulations manager Graeme Lewer said staff had been at a house in September or October last year.
"At that stage the dog was in excellent condition although not registered," Mr Lewer said.
"When we went back to visit the registration had been sorted out and the dog was around the back of the house. We had no reason to view the dog during the second visit."
Mr Lewer described the condition of the dog when it was at the vet as "absolutely disgusting".
"If any member of the public sees or even suspects animals are being ill treated, they need to get in touch with police, council or the SPCA," Mr Lewer said.
"Confidentiality is paramount in these situations and we will endeavour to do our best."
The matter is now in the hands of police.