In pictures: 25,000 dogs line up for Crufts (and 'Scruffts' for mongrels) as officials bow to pressure over hairspray

Crufts, Britain's annual festival of all things canine, opened today with a distinctly international flavour, with more than 2,000 dogs from overseas joining their British counterparts in Birmingham.

In total, more than 25,000 dogs will take part in this year's show. London 2012, with its meagre tally of 11,000 athletes, pales in comparison. Competitors from 41 countries will take part, with dogs from some countries as far afield as India, Indonesia and Malaysia being represented for the first time.

And like the Olympics, Crufts has its controversies over “performance-enhancing” substances.

A blazing row between competitors and the Kennel Club, which manages Crufts, over whether dogs entered into “beauty” events should be allowed to be doused in hairspray, or even touched up with chalk, threatened to derail this year's competition.

Competitors have claimed that a little bit of spray around the head to stop long hair getting in a dog's face was standard practice at other dog shows, but officially it is against decades-old Crufts rules that ban artificial enhancers.

Opponents who organised themselves into a group called the “Elnett revolutionaires”, after a brand of hairspray, said that sending a poodle into competition without hairspray was “like Miss World being made to go on without her make-up.”

In a bid to catch cheats, judges introduced spot-checks in 2011, but have now bowed to pressure and suspended testing. A new code of practice is expected to be in place by next year, for the first time officially permitting hairspray to be used sparingly around the head and face, and for white dogs to be cleaned with a chalk.

In another first, this year's show will be the first to showcase the best of Britain's mongrels, hosting the final of the “Scruffts” competition for cross-breeds for the first time. With pedigree dogs not allowed to enter, the alternative Kennel Club competition has celebrated the more humble qualities of temperament and character in family dogs with mixed heritage since 2000, but has never been a part of the main Crufts show.

Four dogs – the winners of national heats – will go head-to-head for the prize of Scruffts champion tomorrow.

The inclusion of cross-breeds comes five years after the RSPCA withdrew its support for Crufts, responding to a wealth of scientific evidence to show that the selective breeding of pedigree dogs perpetuates inherited health problems. Around one in four pure-bred dogs suffer from congenital defects such as epilepsy, heart disease and hyperthyroidism. Other breeds develop health problems associated with bred-in features. Dachsunds, for example, a particularly vulnerable to spinal problems, while Cavalier King Charles spaniels, which are bred to have skulls that are nearly flat on top, often suffer from syringomyelia, a condition caused by their skull being too small for their brain.

Crufts says that judges are “trained to ensure that only healthy dogs win prizes, which in turn encourages the breeding of healthy dogs.”