Elders in South Australia have been left shocked and devastated by the deliberate destruction of ancient cave art which is up to 40,000 years old.

The Adelaide Advertiser reports vandals wrecked the ancient Nullarbor Plain cave art that is sacred to the Mirning people of the Great Australian Bight.

The designs carved into chalk limestone walls in Koonalda Cave were ostensibly protected by locked steel gates.

An analysis by scientists indicates the significant damage to the art was recent and deliberate.

Nullarbor Parks Advisory Committee chair Clem Lawrie was among the group who discovered the damage.

"It breaks me inside. It's our heritage and it's an internationally recognised site. I was shocked, horrified and disappointed," he told the Advertiser.

Mr Lawrie said more needed to be done to protect sacred sites and he had previously lobbied the state government for better protection.

"There's a whole chain of letters that we sent off… There was no reply from the State Heritage Committee, no reply from the Aboriginal Affairs Department," he said.

First Nations Heritage Protection Alliance co-chair Kado Muir told National Indigenous Times the desecration shows how state laws "fail to empower Traditional Owners".

"It is clear these laws are inadequate for the job of protecting our unique national treasures," he said.

"We are engaged in a co-design process for stronger national heritage protection, that means more involvement and resourcing of Traditional Owners in looking after these important places with cultural heritage management strategies to include public awareness and engagement around the immense values these places represent for the fabric of our national sense of identity and connection to the land and each other".

Speleologist Clare Buswell said the vandals dug around the gates to access the site, carving over the art the words: "Don't look now but this is a death cave".

The cave, listed as a National Heritage site since 2014, features a number of art works. The graffiti has irreparably destroyed art in an area 1.2m by 60cm.

South Australia's current Aboriginal Heritage Act was enacted in 1988, five years before the federal Native Title Act, and Indigenous leaders and other experts have long lobbied for it to be strengthened or replaced by legislation which provides adequate protection for Indigenous heritage.

The federal government recently vowed to overhaul and strengthen Commonwealth laws protecting Indigenous heritage, in response to the findings of the Juukan Gorge inquiry.

More to come.