Tyson, a Lhasa-Chi (cross between a Lhasa Apso and a Chihuahua) was born earlier this year, as part of a litter of five.
The pooch was rejected by his larger siblings at birth - forcing owner Rosemarie McLinden to hand feed Tyson every two hours using a pipette.
McLinden and husband Antony Corr, in Lincolnshire, became anxious when they noticed that their new pint-sized pet began to lose weight after its birth.
The couple rushed Tyson to a vet who couldn't find anything wrong with the canine but gave the pair special feeding instructions as a precaution, 'express.Co.Uk' reported.
"I've been doing a lot of research and I can't see a smaller dog anywhere in the entire country," McLinden said.
Pilgrim Veterinary Surgery Vet Sharon Crocket - who treated Tyson said: "He is so tiny, even for a part Chihuahua. He could possibly be the smallest dog in the UK.
