The federal government has decided not to take action against Adani for its failure to declare its Australian chief executive ran a mining company in Zambia which had pleaded guilty to serious environmental harm.

The ABC reported that prior to approving Adani’s proposed $16bn Carmichael mine in Queensland, the federal environment department wrote to Adani’s Australian head, Jeyakumar Janakaraj, and asked for information about any executive officer who had “been the subject of any civil or criminal penalties or compliance-related findings, for breaches of, or noncompliance with environmental laws ... [and] information about his or her roles both in Australia and in other countries”.

In its response, the company failed to mention that Janakaraj himself had been in charge of a copper mine in Zambia that had polluted a major river with dangerous contaminants in 2010, the ABC reported.

Under section 489 of the Environmental Protection and Biodiversity Conservation Act, providing false or misleading information could be an offence.

The Zambian mine was owned by Konkola Copper Mines, for which Janakaraj was head of operations. KCM was convicted on four charges, including wilfully failing to report the pollution in the Kafue River, the ABC reported. Janakaraj himself was not charged over the contamination.

The federal environment minister, Greg Hunt, approved Adani’s Carmichael mine with the limited information.

A month later ABC revealed KCM’s convictions. The federal environment department then approached Adani to ask why it had not provided this information. The department decided the omission was a mistake and did not warrant further action.

“The Department of the Environment has completed its inquiries into the omission of a component of the environmental history of one of the executive officers of Adani Mining Pty Ltd,” a spokesperson for the department told Guardian Australia over email.

“As a result of these inquiries it was found that the omission did not result in environmental harm, that the omission was likely due to a mistake and that Adani officials provided full cooperation ... In this instance and having due regard to the available responses within the Compliance and Enforcement Policy: Environment Protection and Biodiversity Conservation Act 1999, the department elected to not take further compliance action on this matter.”

Ariane Wilkinson, a lawyer at Environmental Justice Australia, said that “whether or not Adani’s omission to the department caused environmental harm completely misses the point”.

“This was an important omission in checking Adani’s environmental history, something that must take place before approvals are given. Properly considering a company’s environmental history should inform whether or not you give an approval in the first place, and what kind of conditions you apply,” Wilkinson said.

“The department’s weak response is disappointing, but also unsurprising. It’s a good example of why the Australian community needs access to the law to hold decision-makers and corporations to account, and to protect our environment.”

The Carmichael mine remains subject to a challenge in the federal court by traditional owners who say Adani misled the National Native Title Tribunal about how many jobs it would create.

Doubts also remain over whether the mine will get the financing it needs to go ahead. Adani has also asked the prime minister, Malcolm Turnbull, to be given special treatment and protected from further challenges.

If the mine does go ahead, it would produce more annual emissions than New York City, totalling about 79m tonnes of CO2 each year.

An Adani spokesman told the ABC that Janakaraj was committed to proactive and good environmental management.