As wild deer numbers flourish in parts of New South Wales there are renewed calls to declare the animals a pest, which would make them easier to control.

Deer populations have soared by 60 per cent between 2009 and 2016 according to the Invasive Species Council [ISC], the environmental group set up to protect Australia from harmful and invasive species.

Landholders and residents say the animals damage sensitive rainforest and put lives at risk on the state's roads and railways.

Deer are wreaking havoc on Tim Francis's 100-acre property at Foxground in the Illawarra, where numbers are flourishing in the mountainous escarpment, national parks and water catchment.

Mr Francis's property is one of many Landcare conservation projects in the region.

"It's not just foraging for food but marking their territory and also working the velvet off their antlers, ringbarking trees and stripping their bark," Mr Francis said.

"Lots of trees in the past few years have been destroyed by deer. It's a big cost and it's also devastating emotionally to be seeing the damage that's done."

Tree guards and barbed-wire fences are no deterrent.

Fallow deer seen through a rifle scope. ( Facebook: Tasmanian Trophy Fallow Deer & Hunts )

"The deer probably stand a metre or a metre-and-a-half high. They clear our barbed-wire fences without any trouble,'' Mr Francis said.

The ISC said deer were thriving in many parts of the state.

"Deer are probably the most important and emerging pest species in eastern Australia - they are going to be rivalling the extent of pigs, goats and even rabbits eventually but they are much larger," its CEO Andrew Cox said.

Deer were released in Australia for recreational hunting in the 1880s.

In NSW they are considered game animals under the Feral Animal Control Act 2002, which means they can only be shot by licensed hunters with a landholder's permission.

Car written off after striking a large male deer with antlers on the Princes Highway near Wollongong, June 2017. ( Supplied: 97.3 ABC Illawarra Facebook )

The restrictions do not apply to feral pigs or dogs.

However, the conditions have been suspended across nine regions, Tenterfield, Glenn Innes, Port Macquarie, Liverpool Plains, Upper Hunter, Wollongong, Bega Valley, Snowy Valleys and Snowy Monaro.

The NSW Department of Primary Industries said it recognised deer were a threat to primary production, the environment, and the community.

It said it had made it easier to hunt deer by changing the hunting season for several species, allowing the use of spotlights or electronic devices and aircraft as well as watercraft, motor vehicles, baits, lures or decoys. Hunting at night is also permitted.

But some local councils and the ISC argue that these are only short-term solutions.

''Other states have good policies where they declare deer as pests, but they are often not backed by the resources to nip those small populations in the bud," Mr Cox said.

Map showing increase in deer populations across NSW since 2009. ( Supplied: NSW Department Primary Industries )

Wollongong Mayor Gordon Bradbury said the deer had an impact on wetland environments and were also damaging flora and causing soil erosion problems.

"We want it moved from being a game species into a pest species and dealt with accordingly," Cr Bradbury said.

"It's a statewide problem, it isn't isolated to Wollongong."

Cr Bradbury said residents were seeing them in urban areas and public safety was a real issue.

Sydney Trains said there had been more than 30 collisions involving deer wandering onto the rail corridor over the past 12 months, 24 of them in the Illawarra.

More than $1 million was spent on fencing in a futile bid to stop them crossing tracks along the south-coast rail line.

Editor's note (3/10/17): Statistics on the number of people killed in car crashes involving deer have been removed from this article. These statistics formed part of a draft report on the local deer population, but the ABC has been advised they were not published in the final version of the Natural Resources Council report.