Leading animal charities have distanced themselves from Crufts as concerns mount over the welfare of some pedigree breeds.

The RSPCA announced that it was pulling out of Crufts as a result.

The Scottish SPCA echoed its English counterpart's concerns over pedigrees including the King Charles spaniel, saying breeding has resulted in a brain too big for the skull, which can cause the animal excruciating pain.

The RSPCA said it had suspended plans to staff a stand at the world-famous dog show in March 2009, as it has done in the past. It is also calling for new measures to tackle disability, deformity and disease among pedigree breeds.

A television documentary revealed the breeding process of such dogs resulted in a high level of genetic illness.

The BBC programme said the unhealthy, often inbred, dogs were still able to compete in dog shows and had gone on to win "best in breed".

The RSPCA said it became increasingly concerned about the situation in the wake of the documentary, which showed a prize-winning Cavalier King Charles spaniel with syringomyelia - the condition which occurs when a dog's skull is too small for its brain.

The programme also featured boxers suffering from epilepsy, pugs which had breathing problems and bulldogs unable to mate or give birth unassisted.

RSPCA chief veterinary adviser Mark Evans called for a shift in emphasis away from the looks of show dogs towards their health, welfare and temperament.

"Dog shows using current breed standards as the main judging criteria actively encourage both the intentional breeding of deformed and disabled dogs and the inbreeding of closely related animals," he said.

"There is compelling scientific evidence that the health and welfare of hundreds of thousands of pedigree dogs is seriously compromised as a result.

"From a dog health and welfare perspective, such shows are fundamentally flawed and do our much-loved pedigree dogs no favours. Intentionally breeding deformed and disabled animals is morally unjustifiable and has to stop."

Mike Flynn, chief superintendent for the Scottish SPCA, said that, while the organisation did not take part in Crufts, it still had concerns.

He said: "If you look at the 100 or so recognised breeds that there are you are maybe looking at 10-15% that have severe problems, such as the English bulldog, the pug and the King Charles spaniel.

"We have concerns with certain breeds, but not all pedigrees - a lot are fine.

"The King Charles spaniels' brains are too big for the size of the skull, so the brain goes against the spinal column and causes severe pain.

"Bulldogs can hardly walk the length of themselves. They have been bred in such a way that they are shaped to conform to standards and that has caused serious problems."

The RSPCA also wants to see the development of health-focused breeding strategies for individual breeds, including steps to increase their genetic diversity.

More data collection and scientific analysis is needed on the causes of health problems in dogs, as well as education to encourage demand among would-be owners for animals that have the best chance of being healthy, the RSPCA said.

Caroline Kisko, Kennel Club spokesman, said: "The fact that the RSPCA continues to make such unhelpful statements with regard to the health of pedigree dogs is extremely regrettable but we will continue to endeavour to work with them despite their stated position - for the benefit of dogs.

"The Kennel Club is dedicated to improving the health and welfare of dogs through responsible breeding and will continue to use Crufts as a platform to educate breeders and the public."