An emaciated dog believed to be from Bristol was left to die with "horrendous" injuries.
The Saluki lurcher was found with a broken back and skull on farmland off Bewdley Road North, near Stourport-on-Severn, by a farmer on April 5.
He cared for the starved animal until RSPCA inspector Jonathan Ratcliffe arrived at the scene.
At first Mr Ratcliffe suspected the dog - who was bleeding heavily from a head wound - may have been involved in a car accident and rushed him to a vet.
But the vet found the injuries were non-accidental. The dog had dislocated vertebrae as well as the fractures to his back and skull.
The dog was so poorly that the vet put him down to end his suffering.
Mr Ratcliffe said: “The dog was was found at 5pm.
"We suspect that he may have been used in an illegal activity such as hare-coursing the night before or in the early hours of the morning, meaning that he had been left to suffer horrifically for many hours.
“The dog was in absolute agony. It was awful to see.
"In my 12 years as an RSPCA inspector this is one of the worst cases of cruelty I have come across. To leave an animal in such a state of horrendous suffering is despicable.”
Owner believed to be living in Bristol
The dog was microchipped and during his investigation Jonathan was able to make contact with a previous owner.
The details on the microchip were not up-to-date as he found out they had given the dog to a new owner living in the Bristol area.
The RSPCA is now trying to trace that owner and Jonathan is also keen to hear from anyone who may have seen suspicious activity on the night of the incident.
He said: “The dog is a distinctive-looking tri-coloured lurcher who was emaciated and he was also wearing a red collar so I am hoping someone will recognise him and will be able to identify his latest owner who we are confident lives in the Bristol area.
“Also I am wanting to see if anyone saw anything suspicious on the night in question or saw any vehicles in the area which may help me trace the owner.”
Anyone with information should contact the RSPCA appeals line on 0300 123 8018.
To help the RSPCA continue rescuing, rehabilitating and rehoming animals in desperate need of care please visit its website.
