The rock art on the Burrop Peninsula of Western Australia, now a national heritage-listed part of Murujunga National Park, includes an estimated two million ancient carvings, and is a frequent target for vandals.
"Someone has actually etched in to a rock, right above where some of the rock art is, and wrote "Go and work for a living," said tour guide Clinton Walker.
Parliament member Robin Chapple said spray paint and other devices have been used to deface to rock art, noting more needed to be done to instruct the public of the importance of the art.
"A group of international visitors used a texta (felt-tip pen) to write their names and the date and everything else on the rock art," Chapple said. "What we have here is the largest gallery of rock art anywhere in the world. It's the only area of the world that has anything like this."
Defacing rock art is punishable by a fine of 20,000 Australian dollars ($18,802) under Western Australia law.