Crufts dog show started today amid claims that pedigree breeders are "creating a Frankenstein's monster of a dog".
Protesters from People for the Ethical Treatment of Animals (Peta) gathered outside Birmingham's National Exhibition Centre, where the four-day event is held, with banners bearing the slogan: "Hitler Would Be Proud".
The campaigners also displayed posters featuring a white Maltese dog, pictured with a black comb placed across its upper lip to make it look as if it has an Adolf Hitler-style moustache.
The posters are captioned: "Master Race? Wrong for People. Wrong for Dogs. Boycott Breeders. Adopt!"
The group accused the Kennel Club, which runs Crufts, of promoting the breeding of dogs to achieve a "pure bloodline" or "master pedigree" at the cost of animals' health.
Spokeswoman Poorva Joshipura said: "Whether you call it 'pedigree' or 'master race', the quest for pure bloodlines is the same thing - the false and dangerous belief that some breeds or races are superior to others."
She added: "In the race to produce purebred dogs, breeders are moving unwittingly towards creating a Frankenstein's monster of a dog.
"The end result will be not only a more genetically impaired animal but also hundreds and hundreds more homeless animals put to death for the 'crime' of being mutts."
The demonstrations coincide with the publication of an open letter from the producer of a BBC documentary about health problems in pedigree dogs, accusing the Kennel Club of failing to take sufficient action on the issue.
In the letter, published in the magazine Dogs Today, Jemima Harrison said animals "continue to wither genetically" despite the concerns raised in the programme Pedigree Dogs Exposed.
Ms Harrison said: "Some breeds are paying a horrendous price in terms of genetic disease, wounded immune systems and lifespans that, for some, average just six or seven years old."
Her comments come 18 months after the programme sparked concerns by claiming Crufts, the world's most famous dog show, allowed animals bred using damaging practices which cause disease and deformities.
The controversy prompted the Kennel Club and the Dogs Trust to jointly fund an independent inquiry which made a number of recommendations to tackle inbreeding in pedigrees, puppy farming and other welfare issues.
The club later launched a breed information centre on its website to help prospective owners find responsible breeders in their area.
Yesterday the Kennel Club said it was "committed to ensuring that every dog's life is as healthy and happy as it can be".
Caroline Kisko, Communications Director, for the Kennel Club, added: "We are very excited about this year's event, which will celebrate the unique relationship between dogs and their owners and the many ways that they mutually improve and touch each other's lives."
The show features a variety of competitions including the International Agility Championship and the Friends for Life contest, culminating in the Best in Show final on Sunday.
Crufts will be broadcast on More4 this year after the BBC - which began screening Crufts in 1966 - announced it was dropping its coverage in December 2008.
The RSPCA also withdrew its support of Crufts in 2008 because of concerns about the welfare of pedigree animals.