Owner Glenice Bagley claims she rescued her sheepdog Sheba, who is now 178 in human years, when she was just three in 1987 after the animal had been badly neglected following a car crash, 'The Sun' reported.
The 69-year-old retired van driver, who is set to submit an application to the Guinness World Records, said: "I'm proud of her now. If it turns out she's the oldest dog in the world then I'll be even more proud of her.
"She doesn't seem to slow down. She's lovable, she never growls. She'll lick you to death."
Glenice, of Widnes, Cheshire, added: "I got Sheba through my ex daughter-in-law from some people she knew who hadn't been looking after her. They'd had her since she was a pup and she was three at the time.
"I'm always one for a sob story, so I took her in. Now she's 25 and she thinks she's still five. She jumps on the roof of the greenhouse when she sees a cat on the fence. It's a bit of a dangerous trick for an old dog.
"She walks like a youngster -- always at my side with her tail wagging. If she wants to go for a walk she gets up and goes to the door. I'll take her for a walk up and down the street. You'd expect a dog of her age to be too tired, but she never slows down."
Guinness World Records said the oldest living dog they know of is a Mongrel in Italy, born on 1 October 1987. A spokesman said: "A lot of people do say they've got the oldest dog or parrot but have no evidence. As part of the verification process we would require a vet's statement and we try to piece the history of the owner and their dog, including photos of them down the years."