Leaked documents show the New South Wales Government has been warned by its one of own departments that there is a high risk of someone being killed when amateur hunters are allowed into national parks next year.

The Opposition has obtained a 60-page draft risk assessment by the Office of Environment cataloguing the dangers of letting amateur hunters cull feral animals.

It warns the risk of park staff, visitors or other hunters being killed or seriously injured by arrows or bullets is high.

It also finds rotting carcasses left behind could contaminate drinking water and attract feral predators like wild pigs, dogs and foxes.

Labor's environment spokesman Luke Foley says it is a damning assessment that should force the Government to abandon the policy, but he fears it will be ignored.

"I fear that for Mr O'Farrell his dirty deals with the Shooters Party in the State Upper House will trump any responsibility he feels for protecting the safety of the people of New South Wales," he said.

Mr Foley says some of the risks can be reduced but they are impossible to eliminate, and says the Government cannot continue to argue the policy is safe.

"Every government's most sacred responsibility is to protect the safety of their community," he said.

"In the face of this damning assessment by their own office of Environment and Heritage, the O'Farrell government has got no alternative but to abandon the plan to open up our national parks estate to amateur hunters."

Environment Minister Robyn Parker says a full risk assessment will be done before the program starts in March.

"There is already shooting in national parks done by staff and contractors, and risk assessment is undertaken with that," she said.

"Each part [of the program] will have its strict controls and measures."