The Great Dane, named Freddy, lives with owner Claire Stoneman, in Leigh-on-Sea, Essex.
The dog measures 41 inches from foot to shoulder blade and is said to be still growing.
Although no official measurement has been made, Freddy is almost tall enough to take the current Guinness World Record from Zeus, a four-year-old Great Dane from Michigan, US, who is 44 inches tall from foot to shoulder blade.
Freddy is already significantly larger than Britain's current recorded biggest dog Samson, who is 6ft 6in when stood on his hind legs, 'mirror.Co.Uk' reported.
The dog's gigantic size may cause concern to other canines so Stoneman gets up extra early in the morning to take Freddy for his daily walk.
Stoneman said she spends 4,000 pounds a year on standard dog food alone.