India's former environment minister Jairam Ramesh is "absolutely appalled" by the Australian Government's approval of the Adani Group's massive coal mine in North Queensland, which he says will threaten the survival of the Great Barrier Reef, "a common heritage of mankind".

Key points: Australian politicians argued India needs Adani coal to lift poor out of "energy poverty"

Australian politicians argued India needs Adani coal to lift poor out of "energy poverty" Indians "cannot afford" Adani coal, former Indian Ministry of Power head says

Indians "cannot afford" Adani coal, former Indian Ministry of Power head says Adani Group says it is an "absolute and religiously law-abiding organisation"

Mr Ramesh, an elder statesman of India's opposition Congress Party, also said the Federal Government and Queensland Government have failed to do adequate due diligence on Adani Group's environmental and financial conduct in India before granting environmental approvals and mining licenses.

"Adani Group's track record on environmental management within the country [India] leaves a lot to be desired," Mr Ramesh told Four Corners.

"And if it leaves a lot to be desired domestically, there's no reason for me to believe that Adani would be a responsible environmental player globally."

Mr Ramesh said it was almost beyond belief that the Australian Government would look to provide concessional loans and other taxpayer support to facilitate Adani Group's coal mining project — because of the consequences for climate change of developing a giant new mine and opening an entire new coal basin.

"You're giving a tax break to a project that is actually going to have adverse environmental consequences, which will have multiplying effects on weather patterns in the region, across the world. I find it bizarre," he said.

"I'm absolutely appalled by what is happening, because the impact [of climate change] on the Great Barrier Reef is now documented.

"The Great Barrier Reef happens to be in Australia, but it's a common heritage of mankind, it belongs to the world.

"I'm very, very surprised that the Australian Government, for whatever reason, has seen it fit to all along handhold Mr Adani — he is not one of the shining stars of environmental stewardship."

Mr Ramesh said the federal and state governments had failed to do adequate due diligence on Adani's conduct. ( AAP )

Adani coal 'will be too expensive for Indian market'

Australian politicians have argued India needs the coal from Adani's Carmichael mine in North Queensland to lift millions of India's poor out of "energy poverty".

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But another respected Indian observer, the former head of India's Ministry of Power, E.A.S Sarma, dismissed that as false and misguided.

"The Australian politicians are obviously not properly briefed by their offices about the viability of Adani coal," Mr Sarma, who has done a detailed analysis of the properties of the coal at Adani's Carmichael deposit and the economics of its planned mining venture, said.

"My assessment is that by the time the Adani coal leaves the Australian coast, [it] will be about $90 a tonne.

"We cannot afford that, it is so expensive. My assessment is it will not be possible for the Indian market to absorb Adani coal."

He said people in India without access to electricity were, in the main, either too poor to afford electricity, living in remote rural areas where the infrastructure costs of supplying power were extremely expensive, or both.

Former head of India's Ministry of Power, E.A.S Sarma, says it would be risky to provide subsidies. ( ABC News: Wayne Harley )

Coal from the Carmichael venture could not provide electricity at an affordable price for such citizens.

Mr Sarma said it would be risky for taxpayers to provide subsidies or support for the Carmichael mine.

"If I were a finance man in Australia, in the Government, I would not recommend [it]," he said.

"It's a risky proposition — it's actually a subsidy maze.

"You know, you are shifting taxpayers' money into something which is not viable."

Australia urged to do thorough financial due diligence

Mr Ramesh urged the Australian Government to do thorough financial due diligence on Adani Group, amid allegations in India of tax evasion and money laundering, as well as Adani Group's extensive use of shell companies owned in tax havens.

In India, Adani Group's ports business has been hit with a series of adverse findings for environmental misconduct and disregard for the law.

As environment minister, Mr Ramesh commissioned an expert committee to investigate allegations Adani Ports SEZ had violated core conditions of the environmental approval for development of its showcase port and other facilities within a special economic zone it controls in its home state of Gujarat.

The committee found what it called "incontrovertible evidence" Adani had breached environmental clearances — including illegally destroying large areas of mangroves and blocking creeks.

"These were flagrant violations, not accidental violations, but wilful violations, deliberate violations," Mr Ramesh said.

In 2014, the High Court of Gujarat also ruled Adani Group had developed the entire special economic zone, covering a vast area of coastal land, without valid environmental clearance from the national government or coastal regulation zone authorities.

Last year, India's environment court National Green Tribunal found Adani had carried out illegal work on its port at Hazira, in Gujarat's south, "undaunted by [an] absence of environmental clearance or coastal regulation zone clearance" and without "care for any adverse order or adverse impact on environment".

It slapped an Adani company with a fine equivalent to about $5 million, saying its "irresponsible attitude must be deprecated".

Adani have denied any wrongdoing.

In a written statement, it told Four Corners: "The Adani Group is absolute and religiously law-abiding organisation and respect law of the land."

Adani Group accused the expert committee which found it had breached environmental clearances of "a mala fide agenda".

In 2015, after former chief minister of Gujarat Narendra Modi was elected as Prime Minister, his Government issued orders allowing Adani's developments to proceed — despite the earlier findings of the expert committee.

Adani Group has lodged appeals with India's Supreme Court against the adverse court rulings on its operations in Gujarat.