LONDON -- Veterinarians are urging people not to purchase certain breeds of dogs including pugs, bulldogs, Cavalier King Charles Spaniels and shih-tzus.

Breeds such as these are called brachycephalic dogs, and a range of health problems are associated with their characteristic "flat faces".

SEE ALSO:Labradoodle Creator Regrets Breeding 'Frankenstein' of Dogs

The problems arise from the distinctive shape of the dogs' muzzle, head, and throat, which can make it difficult for the animals to breathe. Surgical procedures are often needed to remove obstructive tissues in order to clear the major airway passages.

French bulldogs are one of several breeds known as brachycephalic dogs.Credit: getty images / tom williams

Six different dog rescue companies told the BBC that dogs with squashed faces have been turning up in droves at shelters, including Battersea Dogs Home and Bluecross Animal Rescue, which reported receiving a total of 314 "flat-faced" dogs in 2015.

Mashable Top StoriesStay connected with the hottest stories of the day and the latest entertainment news.Sign up for Mashable's Top Stories newsletterBy signing up you agree to our Terms of Use and Privacy Policy.Thanks for signing up!

Sean Wensley, President of the British Veterinary Association (BVA), said in a quote sent to Mashable, "The surge in popularity of these dogs has increased animal suffering and resulted in unwell pets for owners.

"We strongly encourage people to think about choosing a healthier breed or crossbreed instead.”

In 2015, the UK Pet Owners Association's list of the top 10 most popular breeds in Britain included three brachycephalic dogs: the French bulldog, pugs, and bulldogs.

Tweet may have been deleted

Because the dogs seem to been vogue, puppy farms and substandard breeders perpetuate the problem by trying to meet the demand for the flat-faced dogs.

So perhaps -- for the health of the dogs -- it's best to think twice before picking up that