Traditional owners have lodged human rights complaints against 12 banks over their involvement in Santos' $4.7 billion Barossa gas project.
The grievances are the latest complication for the gas project after the Federal Court last year ruled Santos' approval for it was invalid.
The approval was overturned due to a lack of consultation from Santos with traditional owners.
The Barossa project, north of Darwin, is currently paused and faces increased costs from changes to the federal government's safeguard mechanism.
The human rights grievances have been lodged by six people from the Munupi, Malawu and Jikilaruwu clans on the Tiwi Islands, and one from Larrakia country in Darwin, assisted by Equity Generation Lawyers.
The complaints were made against ANZ, Commonwealth Bank, Westpac, and NAB, for their involvement in a $1.5 billion loan.
Eight international banks and three international export credit agencies have also received complaints.
"Most of these banks have human rights policies, and they have what's called a human rights grievance process," Equity Generation Lawyers associate Vidhya Karnamadakala said.
"[It] invites impacted communities to write to the banks, and to alert them as to the human rights impacts of certain projects that they might be financing."
Ms Karnamadakala said her clients had used the grievance process to tell "the banks that the … project is having a serious impact on their economic, social and cultural rights".
"[They're] asking the banks to withdraw from this loan immediately," she said.
"The fundamental principal in the standard is that businesses should not cause or contribute to human rights impacts."
Paulina Jedda Puruntatameri, a Munupi clan elder, said it was her "aim to stop whoever is supporting Santos with … funds".
"It is our right to protect the sea and the land," she said.
'Difficult to predict' how banks will respond
Last year, traditional owners lost a court battle in South Korea to block loans being sought by Santos' South Korean partner, SK E&S.
The injunction application was an attempt to stop the Export-Import Bank of Korea (KEXIM) and the Korea Trade Insurance Corporation (K-Sure) from providing funds for Barossa.
Ms Karnamadakala said it was "difficult to predict" how the 12 banks would respond to the human rights grievances, but singled out ANZ as one bank which could act.
"ANZ set up its grievance mechanism shortly after it had compensated a number of Cambodian families who were displaced by a sugar plantation company, which ANZ had financed for several years," she said.
"It's clear that these banks have put a lot of thought into these human rights commitments."
An ANZ spokesperson told the ABC it would "consider the matter in line with the processes under our human rights grievance mechanism".
'Cutting edge' issues
Associate Professor Hannah McGlade, a legal academic at Curtain University with special interest in Indigenous human rights, said traditional owners "have the right to free, prior informed consent about business activities impacting their traditional lands and territories".
Despite this, she wasn't aware of an Australian case in which grievances had been filed by First Nations people against financial institutions.
"These are cutting edge human rights issues, reflecting a growing awareness and increasing realisation of the rights of Indigenous people that banks and corporations need to be fully cognisant of," she said.
"States should be enforcing these rights through appropriate legislation and effective enforcement with the participation of Indigenous people."
All financial institutions involved, and Santos, have been contacted for comment.
A spokesman for DBS said it hadn't provided direct financing for the project and "had not been approached to finance the development of the Barossa field".
NAB confirmed it had received the grievance complaint and was working through its contents.
