The revelation puts Labor's promise of no new extinctions at risk and conservationists have called on Environment Minister Tanya Plibersek to pressure her state government colleagues into action.

The evidence was provided to a parliamentary inquiry, which received several hundred submissions, triggered by independent Senator David Pocock in response to reports the Kosciuszko National Park feral horse population had jumped from 14,000 to 18,000 in two years, an increase of 30 per cent.

The Threatened Species Scientific Committee said the wild horses were destroying the delicate alpine ecosystem and could lead to the extinction of 12 species; three frogs, four fish, four reptiles and one mammal.

Six of the horse-affected species are critically endangered, indicating high risk of imminent extinction, while five are endangered.

"Feral horses may be the crucial factor that causes final extinction," the TSSC submission said.

"Feral horses in the alps...pose an imminent threat to the Threatened Species Action Plan's objective to prevent new extinctions of plants and animals."

Due to the "urgency of the problem", the TSSC recommended the Environment Minister lead the state government Environment Ministers in a joint-organisation, to develop a coordinated management of horses across the alps.

For decades, efforts to reduce the Kosciuszko herd have been hamstrung by passionate equine enthusiasts, who believe the brumbies are an iconic part of Australia's history, citing the famous Banjo Patterson poem, The Man from Snowy River.

For the past two decades, there has been a blanket ban on aerial shootings of feral horses in NSW national parks. But several submissions recommended aerial culling as the most effective and humane way to reduce horse populations.

"The acknowledged best practice method to humanely reduce populations of feral horses is shooting (aerial or ground) in accordance with nationally agreed standard operating procedures," the Australian Veterinary Association submission stated.

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The number of feral horses across the nation is estimated at around 500,000, with more than 200,000 in Queensland and the Northern Territory, both of which use aerial culling to control populations.

Many of the pro-horse submissions argued for non-lethal options to reduce the horse population, while also acknowledging such a path would be difficult and ineffective.

The Animal Justice Party lobbied for fertility control, but admitted it would take 10 to 20 years for the population to decline if 50 per cent of the herd were treated, which would be "challenging" to achieve in such a large landscape.

Save the Brumbies stated it was no longer re-homing feral horses "due to the trauma of trucking wild horses over some two days" to the Northern Tablelands, which is more than 1000km away from the Kosciuszko National Park.

"In 2021 we did take 29 horses from KNP; the horses arrived severely stressed, several are still with us in high level care due to injuries and our veterinary costs were substantial," the Save the Brumbies submission stated.

"Due to the above reasons we will not now take horses from KNP."

The federal Department of Environment submission found the NSW government would have to remove 4000 horses annually if it was to meet its target of 3000 horses in the park by mid-2027, as set out in the state's Kosciuszko National Park Wild Horse Heritage Management Plan.

The department's submission also stated "the Australian government does not consider feral horses to have heritage value" and there was an "urgent need" to improve feral horse management at all government levels to "significantly reduce the impact of feral horses in the Australian Alps".

The parliamentary committee is due to hand down its findings by June 9.