It comes as the Invasive Species Council warned the lack of feral horse control is leading to more collisions in the Snowy Mountains and Kosciuszko park between horses and motorists.

No feral horses were removed from Kosciuszko in 2018, a year which saw four collisions between cars and horses.

Environment minister Mick Gentleman said feral horses were a growing threat to Canberra "under the current management plan in our neighbouring states".

Feral horses in Kosciuszko were given "heritage status" by the NSW government last year, limiting population control to non-lethal methods while numbers explode.

At the same time a draft management plan for horses - which in 2016 recommended reducing the then-population from 6000 to 600 in two decades - was thrown out and the state government is in the process of organising a new management plan.

"Latest research shows that feral horses are the largest cause of environmental degradation throughout Australia's alpine parks," Mr Gentleman said.

Canberra's current management plan was last updated in 2007 with the government hoping to have another update later this year.

The council's Reclaim Kosci campaign director Richard Swain said the majority of the collisions since 2011 had been in the Kiandra area, near Selwyn Snow Resort and Yarrangobilly Caves.

"This is a ticking time bomb," Mr Swain said.

He said with more families expected in Kosciuszko's snow fields and the failure to control the horse population, a human fatality was "increasingly likely".

Documents released to the council under freedom of information laws show all collisions between horses and cars in 2018 had occurred in the Kiandra area, with six collisions - with two at the same time - the year before.

The published documents included communications between NSW Roads and Maritime Services and a park ranger, who said feral horses could be "on and around the highway year round".

In an email dated October 25, 2018 the ranger said night time was when most crashes had occurred, with the horses hard to see and not moving off the road.

He said horses tended to be on the Snowy Mountains Highway between the Yarrangobilly Village and the Kiandra and Eucumbene River crossing area.

"There have been near misses throughout this section," the ranger said.

Grisly collision reports provided to the council detailed distressing scenes including one where one motorist had to euthanise a hit foal by bashing its head in with a rock.

The park's risk treatment plan from 2016 - a year they saw only three reported collisions in the Kiandra area - said population reduction would be one of the best control methods to deal with horses.

That same year one driver wrote to the NSW Office of Environment and Heritage and said they encountered about 40 horses on the highway, north of Yarrangobilly.

These documents follow another cache released to the council under freedom of information laws which showed the government's own count of the northern end of Kosciuszko had shown horse numbers had doubled in Kosciuszko.

The council said since the count started in 1998, horse numbers in Kosciuszko park's north, had increased from 75 to nearly 2800.

Kosciuszko's northern section is just across the ACT's border and the ACT government and Canberra's park rangers have their own concerns about an unchecked feral horse population.

The ACT government fears an established population inside the ACT would destroy delicate wetlands which provide the capital with 80 per cent of its drinking water, and the habitats of native species like the critically endangered northern corroboree frog.

The council's chief executive Andrew Cox said the numbers showed the problem was getting worse.

"If you're going to even stabilise the population, you need a far greater number of horses removed. There's a crisis going on," Mr Cox said.

However, the government count the data comes from is criticised as potentially doubling back over the same horses, counting them twice.

Currently the Australian Alp Program, a cross-government group, is conducting their own aerial count with more statistically sound techniques.

But Mr Cox said the last count by the alps program took two years to be released after it had been conducted and action needed to be taken now.