Animal welfare groups said it provided the first reliable figures on what happens to the dogs and exploded the myth that most were kept as pets in retirement.

Abandonment and slaughter were so common that greyhounds’ fate was “a major animal welfare problem”, the report by the National Assembly for Wales said. It prompted calls for legislation to regulate the independent greyhound racing sector and for the industry to meet strict guidelines on the treatment of the dogs.

Researchers said that between 8,000 and 12,000 greyhounds were slaughtered or abandoned annually, of which only an estimated 2,800 were rescued or impounded by local authorities.

The cost to the taxpayer was estimated at £600,000 annually, with lurchers (greyhound cross-breeds used as working dogs) costing a further £1.35 million.

Up to 30,000 greyhounds cease racing each year and animal rights activists have long believed that many are killed or abandoned. The study concludes: “Large numbers of greyhounds and lurchers are abandoned once they are no longer useful. The study shows that the argument that most are kept as pets by their owners cannot be sustained.”

Alain Thomas, of Greyhound Rescue Wales, said the most common methods of killing unwanted dogs were to shoot them or beat them to death. Some corpses had their ears cut off to prevent identification.

Lorraine Barrett, chairwoman of the Assembly’s All Party Group for Animal Welfare, which carried out the study, said: “This report is confirmation of the terrible truth we’ve suspected for a number of years.”

David McDowell, of the RSPCA, said: “There is no justification for abandoning or killing these animals simply because they can’t do their job any more. An animal should be the owner’s responsibility for life, not just until they’ve reached the end of their usefulness.

“It is imperative that the industry finally admits there is a problem and works with welfare organisations to look at ways at tackling this as a matter of urgency.”

Greyhound racing is split between the regulated registered sector, which has 31 tracks in the UK, and the unregulated independent sector, with 21 tracks. The independent sector was singled out for criticism by the report.

Industry representatives, however, dismissed the estimates of killed and abandoned animals as “hugely overblown”. Jeff McKenna, on behalf of independent track owners, said of the figures: “The only reason for euthanasia is if there’s a fatal injury to a dog.

“The majority of independent owners regard their dogs as part of the family. That’s the whole ethos behind independent racing. They are part of the family, not just racing machines.”

Emma Johns, of the British Greyhound Racing Board, an umbrella group for registered tracks, said that the organisation was in contact with animal welfare groups to help to protect dogs, notably the Greyhound Trust, which rehomes retired animals.

“Nobody would say there can’t be improvements, but we have already made many.”

Researchers estimated the number of greyhounds abandoned and killed after conducting a survey of local authorities to establish the number impounded after being found abandoned.

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