ACCESS to national parks could be interrupted over summer as rangers consider ways to protest against the state government's introduction of hunting in NSW's 800 parks.

Anger among National Parks and Wildlife Service staff intensified over Christmas after a leaked draft risk assessment report showed the government will proceed with the plan despite warnings that a fatality or serious injury by gun wound was a ''major risk'' once shooting begins in March.

Rangers will consider walking off the job in the new year but Fairfax Media understands a second and more likely option is parks staff refusing to collect entrance fees as a way to keep parks open and shield the public from the industrial dispute while hitting the O'Farrell government in the hip pocket.

Steve Turner of the Public Service Association said rangers had reached boiling point after the risk assessment listed parks' staff, contractors and volunteers at the top of those at risk of ''projectiles'', including bullets and the arrows of bow hunters.

''They are very unhappy people and really scared about what will happen in March,'' Mr Turner said. ''It's like watching a head-on crash unfold in slow motion. Rangers know the day is coming and, thanks to this risk assessment, they now know how dangerous it will be.''