Rio Tinto has been questioned over royalty underpayments to West Australian traditional owners while facing shareholders at its annual general meeting.
Gumala Aboriginal Corporation believes it could be owed as much as $400 million over a deal struck in 1997 relating to Rio's Yandicoogina iron ore mine in the Pilbara.
Negotiations between Rio and Gumala representatives have been ongoing since 2020, when the mining giant identified underpayments related to the Yandicoogina Land Use Agreement and offered a one-off payment of $40 million.
An independent audit that was subsequently commissioned by the GAC is believed to have put the potential loss at up to $400 million.
GAC's board is understood to have rejected a more recent settlement offer of about $150 million, saying it wants more transparency around how Rio is calculating its figures.
The deal, unlike newer heritage agreements, provides compensation related to ground disturbances in the area rather than sales-based royalties.
GAC executive officer Justin Dhu on Thursday used the AGM in Melbourne to ask why Rio "continue to ignore calls for transparency" in payment disputes.
He suggested Rio had made little progress in repairing relationships with traditional owners, two years after destroying the sacred Juukan Gorge rock shelter.
Rio chief executive Jakob Stausholm said it was "regrettable" there had been underpayments and he was keen to find a commercial solution.
"It was a groundbreaking agreement we made with the Gumala people 25 years ago but of course time moves on and we need to renew that," Mr Stausholm told shareholders.
"You should be aware, certainly from our perspective, this is an absolute top priority, to build and deepen the relationships not just with the Gumala people but with all the traditional owners in the Pilbara. We are working very hard on it."
Mr Stausholm said he intended to travel to Perth this week and had offered to meet with Gumala elders.
AAP understands GAC representatives have been left frustrated by the previous negotiations led by Rio's Perth-based iron ore chief Simon Trott.
They are concerned Rio may have excluded some heavily disturbed areas from its calculations.
Mr Stausholm and outgoing chair Simon Thompson also faced questions over Rio's efforts to mitigate climate change and confronting revelations of widespread bullying, harassment and racism within the global company.
Rio has promised to implement all 26 recommendations from this year's report into the company's culture by former Australian sex discrimination commissioner Elizabeth Broderick.
Perth-based director and former WA treasurer Ben Wyatt was unable to attend, having tested positive to COVID-19 upon arriving in Melbourne.
Having last year faced a shareholder revolt over payouts to its departing executives, Rio avoided a second strike - and possible board spill - with its remuneration report comfortably passed.
The company's climate action plan passed with the support of 84 per cent of shareholders.
Rio's shares were up 0.8 per cent to $111.99 near the close of trade on Thursday.