A report has questioned Adani Mining's suitability to develop a coal mine in Australia because its chief executive has links to an earlier pollution case.
Jeyakumar Janakara was at Zambia's Konkola Copper Mines (KCM) from 2008 to 2013. In 2010, the firm pleaded guilty to water pollution charges.
Environmental Justice Australia (EJA) submitted a report urging regulators to reconsider Adani's Carmichael mine.
Adani Mining called the questioning of Mr Janakara's record baseless. "At no stage has Mr Janakaraj been personally responsible for, or alleged to have been personally responsible for, environmental breaches in Zambia or elsewhere," a statement from Adani said.
The Carmichael coal mine in Queensland has faced widespread opposition from environmental groups. A court temporarily blocked the project because of environmental concerns that two vulnerable animal species would be threatened.
The mine was approved last month.
EJA's report, submitted to the environment department, highlighted the 2010 charges brought against KCM by the Zambian government after it polluted the Kafue river with toxin-laden wastewater.
As KCM pleaded guilty, it was fined 21,970,000 Zambian kwacha (A$4000, $2800, £1870). A group of 1800 Zambians are now suing KCM and its parent company Vedanta in the UK's High Court.
The claimants allege that pollution from KCM's mine led to the destruction of farmland and caused illness. Mr Janakaraj was KCM's operations manager in 2010 when the company was prosecuted.
He had been promoted to chief executive by the time he left for Adani Mining in Australia in 2013. "The fact that someone who has been in charge of a company with so many serious allegations, as well as criminal convictions, in relation to its environmental record now occupies the leadership role in the Adani Group's Australian operations is a compelling reason for the Australian regulators to investigate this issue," EJA's report says.
But Adani's spokesperson told the BBC that questions relating to KCM operations should be directed to the parent company, Vedanta Resources. "Mr Janakaraj has taken responsibility for managing legacy issues and implementing world-standard improvement and capital projects," the statement said.
Australia's Environment Department said it was seeking more information about the the EAJ's report. "The Department has received claims from an NGO about the environmental history of a company operating in another country, which has employed a now current executive of Adani Mining," it said in a statement.
"The Department is seeking clarification from Adani Mining about this matter... [and] provisional advice is that this new information would not materially affect the validity of the [mine's] approval decision."
The Carmichael project is worth some A$16bn ($12bn; £8bn) and will dig up and transport about 60 million tonnes of coal a year for export, mostly to India. It will be situated in the Galilee Basin in the central Queensland region and cover an area seven times the size of Sydney Harbour.
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