Authorities in Australia are planning a controversial cull of more than 5,000 wild horses to effectively wipe out the Snowy Mountains region’s famous brumbies, a breed believed to have descended from mares and stallions brought over by the British settlers 200 years ago.

In a move described by critics as “horrific”, the state government of New South Wales revealed it plans to eventually reduce the population of brumbies in the rugged Snowy Mountains region, south-west of Sydney, by 90 per cent.

The cull will involve ground shooting, trapping, mustering and fertility control but will avoid methods regarded as excessively cruel, such as aerial shooting from helicopters or allowing locals to round up the horses using ropes.

Mark Speakman, the state’s environment minister, said the brumbies in the alpine region have been endangering native flora and fauna and damaging sensitive waterways.

"Horses are an introduced species that are competing with Australia’s native animals and flora in the national park and their numbers are out of control," he said.

Australia is believed to have between 400,000 and one million brumbies spread across the mainland, making up the largest population of wild horses in the world.