Calls for the Western Australian Government to strengthen cultural heritage laws have been renewed in the wake of Wintawari Guruma Aboriginal Corporation’s (WGAC) allegations of mining giant Rio Tinto dumping heritage materials from Marandoo mine into the Darwin tip in the 1990s.

In their submission to the Juukan Gorge inquiry, which was made public on Friday, WGAC alleged the accidental disposal of heritage material taken from the Marandoo mine, formerly Manganese Gorge, led to Rio Tinto, their contractor Kinhill Engineers and the WA Aboriginal Affairs Department conspiring to dispose of the remaining materials and all associated documentation in the same tip.

By 1997, bags of heritage material with unknown cultural artefacts had been discarded at the Darwin rubbish dump. Eastern Guruma Traditional Owners were never told about the loss of their cultural heritage artefacts.

University of Western Australia professor, senior archaeologist and heritage commentator Peter Veth was involved in the survey of the Marandoo site prior to the mine.

He told Guardian Australia the WA Government must take serious action to ensure such a mistake never happens again like the ones at Marandoo and Juukan Gorge.

“The State has to show leadership. It’s a really tough portfolio. It’s big money. And if they can’t get the compliance right in an area worth tens-of-billions-of-dollars — and of the Pilbara, which is one of the great heritage estates in the world — then we’re not a modern State,” he told Guardian Australia.

“We’re locked in the ’50s.”

In January 1992 Traditional Owners organised a six-day survey of the area.

Veth revealed to Guardian Australia that a senior colleague had begged with Rio Tinto, then Hamersley Iron (HI), to postpone plans for the mine until a more thorough investigation of sites had occurred. It was estimated there were at least 400 cultural heritage sites in the area.

“It required a different scale of excavation, of collection, of recording, and that wasn’t allowed to happen in a normal process … because the State and HI basically took a very aggressive line,” Veth said.

Rio Tinto was given Section 18 consent under the Aboriginal Heritage Act 1972 (WA) on February 2, 1992.

Three days later, the Aboriginal Heritage (Marandoo) Act 1992 was passed, allowing the miner uninhibited use of the 193 square kilometre area and protected them from any legal resistance from Traditional Owners.

“This was the only time that such a heavy-handed measure has been taken to remove all protections for Aboriginal heritage within an area of land in Western Australia,” said WGAC in their submission.

“WGAC does not know of anywhere else in Australia where a government has removed heritage protection from an area of land and permits unregulated destruction of cultural heritage.”

WGAC noted in its submission it is this legislation that enables the continued operation of the Marandoo mine, almost three decades later.

In a statement, Rio Tinto Iron Ore chief executive Simon Trott said the company was “not proud” of many parts of their history at Marandoo and reiterates their apology to the Eastern Guruma people.

“We know we have a lot of work ahead to right some of these historical wrongs which fell well short of the standards we expect today. This will take time, consistent effort and open dialogue with the WGAC to rebuild trust and reset our relationship for the future,” he said.

“Our leadership team are engaging regularly on this important work and are committed to meeting with the WGAC again when they are ready.”

Trott also said Rio Tinto supports the repealing of the Marandoo Act and that the miner has been working alongside both Traditional Owners and the WA Government on the issue.

“We have committed to all Traditional Owners on whose land we operate in the Pilbara that we will modernise our agreements with them,” he said.

The WA Government’s current position is that it had no previous knowledge of the allegations in WGAC’s submission, and Aboriginal Affairs Minister Stephen Dawson has now said the Government will look to repeal the Marandoo Act.

In their submission WGAC said what occurred at Marandoo in both 1991 and 1992 was “devastating”.

“The losses of cultural heritage sites were unprecedented in scale, combined with the arrogance of HI and the steamrolling actions of both HI and the State Government demonstrates the true powerlessness of Aboriginal people in the Aboriginal heritage approvals system,” they wrote.

“It is a wound that has not healed — that so many cultural sites were lost, blasted into fragments, without even a record, note or photograph kept. To make way for the mine Manganese Gorge and the Country around it was destroyed completely. Nothing remains today beyond a deep hole in the ground.”

By Rachael Knowles