A Namadgi ranger called ACT Policing's rural patrol team to the Orroral camp ground south of Canberra at about 11am yesterday after discovering the wreckage.

Namadgi National Park manager Brett McNamara said it was the worst case of vandalism deep within the park he'd heard of in two decades.

''With Christmas and the festive season, the last thing we'd expect would be such blatant acts of vandalism occurring in a very remote part of the ACT,'' he said.

The camp ground might need to remain closed into the new year unless contractors can be found in the week before Christmas.

''From what I understand talking to staff it sounds like a blatant act of vandalism, to put it mildly,'' MrMcNamara said.

The wooden walls of the large public toilet block were ripped from the structure, sinks were pulled out and toilet basins torn from the floor.

A gushing pipe had flooded the block by the time rangers and police arrived.

A picnic table and sink were thrown into a fire pit and set alight.

Fire extinguishers were also removed and scattered across the camp ground.

It is not yet clear how much the repairs will cost.

''We'll have to get the assessors out there on Monday, if we can get them out obviously with Christmas and the Christmas shut-down period,'' Mr McNamara said.

''It certainly would be a significant cost to the park, but its also a cost in terms of the inconvenience to campers in the area, and also obviously an inconvenience in terms of repairs.''

Rangers found the site undisturbed on Friday afternoon while on a cleaning run.

Police are investigating the incident, and the camp ground has been made safe.

Mr McNamara said security would be ramped up over the Christmas period.

For more, pick up a copy of today's Canberra Times