ADANI once claimed its mega mine in Queensland would lift millions of Indians out of poverty by providing them with cheap electricity but it has now been accused of ripping off citizens through a complex fraud.

The controversial mining giant, which is trying to get a $1 billion taxpayer loan in Australia to help build its giant mine in Queensland's Galilee Basin, is being investigated in India for allegedly siphoning 15 billion rupee ($298 million).

Details of the alleged fraud are contained in a Directorate of Revenue Intelligence file compiled in 2014 and published in The Guardian today. It sets out how Adani allegedly inflated invoices for an electricity project in India so it could shift huge amounts of money into offshore bank accounts.

If true, this would have reduced taxes Adani paid and would likely have led to higher power prices for Indian consumers.

It's believed the DRI has passed the allegations on to the Indian agency that investigates financial crimes, the Enforcement Directorate.

But it's unclear what the status of these investigations are. Adani has said the case is before the Adjudicating Authority.

Last year, six Adani subsidiaries were among 40 other countries being investigated for allegedly inflating the price of coal imports in Indonesia to hide profits in overseas tax havens.

Concern over Adani's dealings overseas, including illegal dealings, bribery, environmental and social devastation as well as allegations of corruption, fraud and money laundering has already been raised by Environmental Justice Australia in a report released in February.

Adani's project in Australia has been controversial because of potential impacts on the Great Barrier Reef from extra coal shipments nearby and the impact emissions from the burning of the coal would have on climate change, which is the biggest threat to the reef.

While politicians have spruiked the jobs that will be created by the mine, there's been concern over whether it should be granted a $1 billion taxpayer-funded concessional loan to build a railway line to transport the coal to the port at Abbot Point for shipment overseas.

GetUp! said the fraud allegations revealed today demonstrate the enormous risk to Australian public money if the Northern Australia Infrastructure Fund decided to approve the taxpayer-funded loan to Adani.

"Prime Minister Turnbull and Queensland Premier Palaszczuk must immediately rule out public money being given to this disgraced company for its dangerous coal project," GetUp! environmental campaign director Sam Regester said.

CONGRATULATIONS: Rockhampton Mayor Margaret Strelow shakes hands with Adani chairman Gautam Adani. Contributed

Environmental Justice Australia lawyer David Barnden said NAIF was compelled to take account of reputations when it considered loaning money to a project.

"With all that is known about Adani's activities and how much the Carmichael project's coal would add to the world's climate problem, it is inconceivable that a loan for the project would satisfy NAIF's requirement not to damage government reputations," he said.

"NAIF has no option but to suspend consideration of any loan to the Galilee Basin railway project until investigations in India are resolved."

WILL THE LOAN GO AHEAD?

NAIF spokeswoman Carol Belletini told news.com.au it would not comment publicly on the specifics of any project.

"As you are aware the NAIF treats business information regarding the status of potential investments as commercial in confidence," she said

"This is in the public interest as it enables NAIF to maximise the public benefit in its negotiations including broader economic and population growth that will be generated from the projects NAIF supports."

Ms Belletini said the NAIF Board was well aware of its duties and obligations in considering and making any investment decisions.

"Without commenting on any specific project in NAIF's pipeline we point out that because a project has moved into a due diligence phase it does not follow that NAIF is actively engaged in due diligence," she said.

"NAIF operates under a proponent-led model. This means NAIF does not control the timing of the due diligence and the provision of information by a proponent. NAIF will assess all relevant matters at an appropriate time."

There has been controversy over NAIF's decision making process, with a Senate inquiry set up to investigate the governance and transparency of the processes used to appoint board members, including whether there is an assessment of potential conflicts of interest.

Corporate governance expert Thomas Clarke said it was unheard of for a publicly-funded body to operate in such conditions of "absolute secrecy".

Last week Greens leader Richard Di Natale threatened to haul every NAIF director before a Senate inquiry over its dealings with the Adani mine.

During a Senate inquiry in Canberra on Friday, Senator Di Natale asked NAIF chief executive Laurie Walker why it hadn't been quashed when Adani said the government loan was "not critical" for the project, one of the criteria that projects are judged against.

"It'll be a matter for the board at the time they are assessing a project," Ms Walker said.

Senator Di Natale was not satisfied by the response and vowed to haul every NAIF director before the committee.

"Today's hearing shows the board has advanced the Adani project against their own investment rules," he said.

WHAT DID ADANI ALLEGEDLY DO?

The allegations against Adani include that it used a Dubai front company to order hundreds of millions of dollars worth of equipment for an electricity project in India, which it then sold back to Adani-controlled businesses for a massively inflated price.

This meant Adani spent an average 400 per cent more for the materials, and because tariffs for electricity transmission networks in India are partly based on what they cost to build, this would have pushed up prices for consumers.

A significant amount of the money was allegedly siphoned out of the country was provided by Indian taxpayers through loans provided by the publicly-owned State Bank of India and the private bank ICICI.

Adani has denied the allegations of overvaluation and said it was fully cooperating with the DRI investigation.