London - The American bully has become a fearsome status symbol in some of the world's inner-city areas.
But dog experts warn unscrupulous breeders are creating a menace.
The American bully is a recognised breed in the US, but not in the UK, and it is thought many puppies sold in Britain are a mix of varieties.
Bill Lambert of the Kennel Club warned that cross-breeds could be "dangerous". He said: "When you cross breeds to create new ones ... you do not know the temperament."
Dog behaviourist Colin Tennant, who has worked with American bullies, said: "They appeal to a section of the population who like to strut about with a big, muscular dog at the end of a lead."