The Federal Environment Department says Indian mining giant Adani likely made a "mistake" when it failed to disclose that its Australian chief executive ran a mining company in Africa that pleaded guilty to serious environmental harm.

The ABC revealed in November that Adani Mining's Australian head, Jeyakumar Janakaraj, was in charge of a Zambian copper mine when it discharged dangerous contaminants into a major river in 2010.

The company that owned the mine, KCM, was convicted on four charges, including wilfully failing to report the pollution in the Kafue River.

At the time, Mr Janakaraj was KCM's director of operations and was described in parent company documents as "responsible for overall operations of KCM", but he was not charged in relation to the contamination.

Mr Janakaraj left KCM for Adani in 2013.

In August 2015, the Federal Environment Department wrote to Mr Janakaraj seeking "information about environmental history of [Adani's] executive officers" as part of its assessment of the Indian company's proposed $16 billion Carmichael coal mine in central Queensland.

The letter, obtained by the ABC, asked the company to provide information about any executive officer who "has been the subject of any civil or criminal penalties or compliance-related findings, for breaches of, or non-compliance with environmental laws...[and] information about his or her roles both in Australia and in other countries".

But in its response, Adani failed to disclose the Zambia incident and Mr Janakaraj's role with KCM at the time.

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Scrutiny of Adani's environmental history 'inadequate'

Two months later Federal Environment Minister Greg Hunt approved the Carmichael mega-mine for a second time with "36 of the strictest conditions in Australian history".

But after the ABC revealed in November that Mr Janakaraj had been the director of operations of the KCM mine in Zambia when the Kafue River was contaminated, the Environment Department admitted that it had not been told of the incident.

The day after the ABC's report, the department asked Adani why the information had not been disclosed during the assessment process for the Carmichael mine project.

The department has told the ABC that it has now completed its inquiries into the omission, finding it "was likely due to a mistake and that Adani officials provided full co-operation … [and] the omission did not result in environmental harm".

The department has "elected to not take further compliance action on this matter … [but] Adani Mining Pty Ltd has been reminded of its obligations under the Act to provide accurate information to departmental officers".

Environmental Justice Australia, which alerted the department about Jeyakumar Janakaraj's time in Zambia, has criticised the department's response.

"It remains our position that the scrutiny of the Adani group's environmental history has been inadequate," Environmental Justice Australia lawyer Ariane Wilkinson said.

"The Australian public rightly expects that these issues aren't just glossed over.

"It is about the department having the correct information to bring adequate scrutiny to the environmental history of the Adani group before approving environmentally risky projects, like the largest proposed coal mine in Australian history."

An Adani spokesman told the ABC that the company and Mr Janakaraj stood by their earlier comments that Mr Janakaraj was committed to proactive good environmental management.