Any failures in a NSW culling program to halt feral horse damage in Australia's high country will spark federal intervention.
The government has flagged a "zero-tolerance" approach to feral horses in Kosciuszko National Park if NSW's plan of attack fails.
The state has legislated to cut the population to 3000 by mid-2027, a vast reduction on recent population estimates of over 22,000.
In response to a parliamentary inquiry on the issue, the federal government backed the cull, but with a warning.
"Should this be insufficient to avoid further irreversible damage to matters of national environmental significance and the Australian Alps, the Australian government would seek the further reduction of horse numbers and support a zero-tolerance approach, such as that currently employed by the ACT," it said.
The ACT's Environment Minister Rebecca Vassarotti says that was effectively a pledge to pursue eradication.
In the ACT there are no established feral horse populations in Namadgi National Park but on occasion they have crept over from neighbouring Kosciuszko.
The ACT's response is always to find them and kill them.
The Invasive Species Council says the federal government has made it crystal clear the environmental damage must stop.
"This is a clear statement from the federal government that NSW needs to seriously consider moving towards eradication," advocacy director Jack Gough says.
Federal Environment Minister Tanya Plibersek has long said horses don't belong in Kosciuszko National Park and they are pushing unique native species towards extinction.
The Threatened Species Scientific Committee says horses in the Alps are threatening the survival of species of three frogs, four fish, four reptiles and one mammal.
Their hard hooves and grazing habits degrade stream, bog and grassland habitats.
The committee says they pose an imminent threat to the government's objective of preventing new extinctions.
NSW Environment Minister Penny Sharpe says the parliamentary inquiry found what everyone already knows.
"Wild horses are damaging Kosciuszko National Park,'' she said.
"Our focus in NSW is getting down the number of wild horses in the park as humanely and as quickly as possible."
