Conservation groups have slammed the NSW government's plan to protect brumbies in the Snowy Mountains, claiming it will put at risk dozens of native species.
NSW deputy premier and Nationals leader John Barilaro will this week introduce legislation to parliament recognising the "heritage value" of the brumbies.
The proposed laws would prohibit culling of the brumbies in the Kosciuszko National Park if passed.
The decision comes a few weeks after an independent committee found feral horses in the Alpine region were endangering more than 20 plant species and seven animal species, including three endangered frogs.
It's estimated more than 6000 feral horses occupy about half of the 700,000-hectare Kosciuszko National Park.
Mr Barilaro said he has always opposed "cruel forms of culling" and has advocated for non-lethal ways of managing brumby numbers.
He said on Sunday that brumbies found in "highly-sensitive" alpine areas of the national park would be relocated by authorities.
But the National Conservation Council branded the move a "grotesque" misuse of environmental law.
Chief executive Kate Smolski said the brumby was the "most destructive pest species" in the state's fragile alpine areas and is destroying vulnerable wildlife.
"These species occur nowhere else and if the damage caused by feral horses does not stop we may lose them forever," she said on Monday.
"It is critical that we control their numbers in our alpine areas, and it must be done as humanely as possible."
The National Parks Association of NSW accused the government of valuing introduced species over native wildlife.
"The decision is an international embarrassment," chief executive Alix Goodwin said.
The NSW Greens agree wild brumbies were having a negative impact on the environment and their numbers needed to be reduced, but want better control methods.
"The reality is, we cannot shoot our way out of this problem; we need sustainable and humane wild horse population control measures, ensuring that we also protect Kosciuszko's pristine natural environment," the party's animal and environmental spokeswoman, Mehreen Faruqi, said.
Deakin University Professor Don Driscoll on Sunday labelled the government's announcement a "disaster" to Australia's heritage.
"It's also cruel to thousands of horses because of the escalating population that will starve to death due to the decline in food resources," he said.
The bill will lead to a research and monitoring program, a brumby count and a marketing campaign to promote rehoming and adoption of the animals that need to be removed from the park.
In addition to the bill, Environment Minister Gabrielle Upton has approved horse riding in four national parks - Kosciuszko, Deua, Monga and Mummel Gulf - following a two-year trial.
