Indian billionaire Gautam Adani's mammoth Carmichael mine, in central Queensland, is pledged to bring with it 10,000 jobs and $22 billion in taxes and royalties.

Undoubtedly this is a project of national significance. It promises to open the vast inland Galilee Basin. To allow that to happen there is a need for a new coal rail line, hundreds of kilometres long, from the mine to Abbot Point Port north of Mackay. There an already-substantial coal terminal will be expanded to handle Carmichael's huge output.

But the significance of Adani's mine, if constructed, is not just the economic boon that producing up to 60 million tonnes of coal a year would bring – increasing Queensland's coal production by one-third and as much as doubling the state's thermal coal exports – but also that the coal will be shipped through the Great Barrier Reef to India.

The project faces massive political uncertainty in the wake of the seismic state election result, just as a Fairfax Media investigation has unearthed details about Adani's business dealings - including fraud allegations, the use of tax havens and issues of transparency - that some argue mean the endeavour warrants much greater scrutiny.

The development, the subject of promises of lavish taxpayer subsidies from ousted premier Campbell Newman and his deputy Jeff Seeney, is a battleground for whichever party strikes a deal with the crossbench to form a probable minority government.

Annastacia Palaszczuk, whose Queensland Labor Party achieved one of the biggest swings in Australian political history at last Saturday's Queensland election to oust the LNP government, has vowed a Labor government would scrap taxpayer subsidies for any Galilee coal-related project, including Adani's.

There are now questions over that pledge.

At least one crossbencher, on whose vote a minority Palaszczuk government could depend, Katter's Australia Party leader Rob Katter, backs government investment in Galilee infrastructure. He has even flagged it as a possible deal-breaker if Labor won't help fund the planned rail line linking new coal developments in the basin to Abbot Point.

"We can unlock 28,000 jobs in the Galilee Basin if we get this railway happening," he told Fairfax Media.

Newman and Seeney had promised an undisclosed sum, of hundreds of millions of dollars of taxpayer funds, to help Adani build the rail line, on the condition it would share the railway with other mining companies that plan to develop in the basin.

Senior federal government ministers have hailed Adani's plans as a lifeline that would lift 100 million Indians out of poverty.

Adani issued a statement this week declaring the Queensland election result would not influence the company's financial decision making – that the plan to build Australia's biggest coal mine would proceed regardless.

It is against this backdrop of political flux that questions have emerged about the transparency of the operations of a company that has received tremendous political goodwill since it secured a 99-year lease at Abbot Point Port for $1.8 billion in 2011.

Fairfax Media has found a complex web of companies tied to Adani's Australian coal developments, extending from the low-tax regime of Singapore to the tax haven of the Cayman Islands. Company documents also suggest uncertainty about the ultimate ownership of the Abbot Point development, which has attracted global scrutiny and fierce criticism from the environmental movement because of its closeness to the Great Barrier Reef.

Fairfax Media is not suggesting there is anything illegal about Adani's complex corporate structure. But its use of offshore, low-tax jurisdictions in relation to itsAustralian operations, and the apparent uncertainty about ownership of the Abbot Point Port lease, raise questions about the ability of the public to scrutinise a project of such huge economic and environmental significance.

Gautam Adani, who has close ties to India's newly elected Prime Minister Narendra Modi, has been the public face of his company's Australian operations.

Most recently, he attended the G20 summit in Brisbane in November, after which the company signed a memorandum of understanding with the State Bank of India for a loan of up to $1 billion to help fund the Carmichael project.

It appears that Gautam Adani does not ultimately control many of the companies associated with his company's Australian coal developments. Instead his eldest brother Vinod Shantilal Adani holds pivotal positions.

Vinod has been named in an Indian criminal investigation into the alleged siphoning of $1 billion from Indian shareholders in three Adani companies into offshore accounts.

The allegations, widely reported in Indian media and confirmed to Fairfax by an investigator in India's Directorate of Revenue Intelligence, stem from an import scheme in which three Adani companies are alleged to have imported power equipment at an inflated price, with the excess sum siphoned into a Mauritius entity controlled by Vinod Shantilal Shah – an alias for Vinod Shantilal Adani.

In Indian media reports, Adani company officials have denied any wrongdoing and have described the allegations as "politically motivated" and a move to resurrect old cases.

Whatever the truth of the untested allegations, a trail of documents appears to tie Vinod Shantilal Adani to the ownership of the Abbot Point lease.

One of the difficulties in following Adani's corporate trail is conflicting paperwork.

The Abbot Point Port, for example, which has been controversial because of a now-abandoned plan to dump dredged spoil near the Great Barrier Reef, is one such example. Company documents, including annual reports filed in India, say Adani Enterprises – the Bombay Stock Exchange-listed parent company for a network of related Adani entities – had divested, or sold, its interest in Abbot Point Port in 2013 for $235 million to a private company in Singapore called Abbot Point Port Holdings.

A company record lodged in Singapore names Abbot Point Port Holdings' sole director as Vinod Shantilal Adani.

But records held by the Australian Securities and Investments Commission, and annual reports for Adani's registered Australian companies, continue to name a publicly listed Indian company, Adani Ports and Special Economic Zone, as the ultimate shareholder for the port.

Adani Ports and Special Economic Zone is majority-owned by Adani Enterprises.

Meanwhile, the company that has mostly interacted with the Queensland and federal governments has been another subsidiary of Adani Enterprises, Adani Mining Pty Ltd.

A spokesman for Adani said Adani Ports and Special Economic Zone retained the lease to Abbot Point, but there had been an "intention to change ownership structure".

North Queensland Bulk Ports and the Foreign Investment Review Board had approved a "proposed transfer of ownership of the lease itself" but this had not taken effect yet, he said.

When asked to explain the apparent inconsistencies between Adani's Indian and Australian records, and to clarify who owned Adani's stake in Abbot Point terminal, the spokesman said Fairfax Media was "baselessly suggesting Adani is seeking to obscure the ownership arrangements for the lease at Abbot Point".

"The Indian filings you refer to with respect to ownership arrangements reflected the intention to change ownership structure which was pending, as was advised at the time. This is consistent with an obligation to disclose market-sensitive information promptly. Any suggestion that this is inconsistent with, or in conflict with, the extant ownership arrangements is categorically incorrect," he said.

When asked, neither the Queensland government nor Treasurer Joe Hockey, whose department has carriage of foreign ownership issues, would answer a list of questions about who controlled the Carmichael project, citing confidentiality. However, federal government sources confirmed they were aware of a plan to transfer ownership, but it had not been concluded.

Fairfax Media's questions were put to the Queensland government before the election through the office of Deputy Premier Jeff Seeney, who as Minister for Infrastructure and Planning has had oversight of the Queensland approvals for the Carmichael project.

Environment Minister Greg Hunt, who signed off on the federal environmental approvals for the mine and rail, said the matter should be referred to Labor.

"The Queensland ALP opened the Galilee Basin and allocated the tenements," Mr Hunt said.

"This has always been their project. Thirty-three of the 34 key approvals under federal law were made under federal Labor."

Then there is the subject of tax, which is a sensitive topic at the moment, with a Senate inquiry under way into tax avoidance, focused especially on multinationals.

Company documents lodged in Singapore show Vinod Shantilal Adani is the sole director of three more vehicles established in the low-tax regime that appear to have links to Abbot Point and the Carmichael rail line.

ASIC records show Adani began assembling a new group of companies around a Singapore vehicle, Carmichael Rail and Port Singapore Holdings, on August 28, 2014.

Vinod Shantilal Adani is also named as a representative of the company listed as the ultimate shareholder of the Singapore vehicles, called Atulya Resources Limited – based in the well-known tax haven the Cayman Islands.

It is not unusual for companies to make use of entities in low-tax jurisdictions. However, the use of such vehicles has come under increasing scrutiny in recent times, with a global push for more transparency.

Adani insists there is nothing untoward about this arrangement.

"Ownership structures of the companies reflect the required level of ring-fencing and financial governance architecture required for a mine, rail and port project, and T1 (Abbot Point) port operations. The above is also layered to meet the various regulatory and funding regimes that apply to these assets," Adani's spokesman said.

Any suggestion of irregularities or non-compliance was "fanciful", he said. He added it was unnecessary to respond to allegations about Vinod Shantilal Adani.

"The claims about ownership structures that are based on this premise, having been shown to be incorrect, don't follow," he said.

"This is unfortunate. Having emphatically rejected the premise of these falsehoods, it is self-evidently unnecessary to rebut supplementary falsehoods."

Tim Buckley a director at the Institute of Energy Economics and Financial Analysis (IEEFA), a not-for-profit that conducts research on financial and economic issues related to energy and the environment and has conducted research for Greenpeace on Adani, questioned whether appropriate government checks had been done.

"The 2014 Adani Ports annual report clearly highlights the divestiture of Abbot Point Port was undertaken at the end of 2013," Buckley said.

"There is no reference to this transaction failing to proceed or being reversed, therefore it is a mystery to me how Adani's representatives can claim this transaction hasn't proceeded, without clear notification to the Bombay Stock Exchange and the Australian authorities."

Buckley said checks should have monitored the reported transfer of interests in a large Australian port from a known large listed Indian company to "a previously unknown string of private companies established in a number of offshore tax havens operated by directors with no known prior operations in Australia."

Jeffrey Knapp, an accounting expert at the University of NSW, said the accounting practices of Adani in India and Australia were "dubious".

Knapp noted that Adani Enterprises excluded the Australian companies for the Carmichael project from its accounts of 2013 and 2014, on the basis they would be disposed of in the near future.

"But nearly two years later they still have control and two years later is not the near future according to the relevant Indian accounting standard," he said.

Adani appeared to be getting companies out of the group picture for accounting purposes, he said.

The picture casts a further shadow on a project that some analysts, including Buckley and UBS global commodities analyst Daniel Morgan, have warned is unviable when coal prices are plummeting and bankers have been reluctant to finance the Galilee Basin.

Concerns have extended to how the Adani group of companies, with their rising debt levels, will finance the Carmichael project, while Greens leader Christine Milne warned last year the project was "a stranded asset in the making".

In India, opposition MPs have worried about Prime Minister Modi's close ties to Gautam Adani and have questioned state funds being used to bankroll a project many view as unviable.

This week, Adani announced another large restructure in India that would leave Adani Enterprises to focus on mining, while its port and power interests would be moved into listed port and power subsidiaries.

Buckley said the restructure suggested Adani could be moving to align its power business with the position taken by India's Energy Minister Piyush Goyal, who has flagged that India might be able to cease thermal coal imports in two to three years, because of a focus on domestic coal production and renewables.

Last month, Adani Enterprises announced it planned to invest up to $4 billion in a solar panel plant in a joint venture with solar power firm SunEdison.

But the Australian government's defence of Adani's plans in Australia has been steadfast.

Trade Minister Andrew Robb moved recently to dispel doubts about the Carmichael project.

Mr Robb said not only had Gautam Adani's development proposals for the Galilee Basin cleared strict Australian environmental standards, but his business plans had also passed the test.

"The business plan [has been] put in front of us," Robb said. "In the end the commercial judgments are Adani's. [But] he strikes [me] as one of the most passionate entrepreneurs I've come across, and that's a big statement, because there are a few passionate entrepreneurs around."

Robb told Fairfax Media this week: "Any government in Queensland you would expect would continue to support this project, out of recognition for the significant economic benefits it will bring to the state, including the thousands of jobs it will help create."

Other federal government sources believe state government support for the rail projects makes a lot of sense, because an equity stake in the rail would give the state a say in how it was operated.

They also believe it would reduce the financial hurdle for companies looking to open up the basin, resulting in more jobs and royalties.

Robb and Prime Minister Tony Abbott have signalled a free-trade agreement between Australia and India this year is a priority.

But as the world opens up to India, questions of corporate governance structures will become more pressing.

Abbott, who faced an onslaught of criticism from environmentalists after declaring "coal is good for humanity", told an annual minerals industry dinner last May it was Australia's "destiny" to "bring affordable energy to the world".

While in India in September, he singled out Adani's Carmichael project for praise: "It's one of the minor miracles of our time – that Australian coal could improve the lives of 100 million Indians, and it just goes to show what good that freer trade can do for the whole world."

Other ministers, including Hunt and Hockey, have also championed the project, or Australian coal exports in general, as a solution to energy poverty.

But in the aftermath of the Queensland election, observers, including the progressive think tank The Australia Institute, have asked why an Indian mining company stood to benefit from the support of Australian taxpayers.

The most recent financial disclosures lodged with the Australian Electoral Commission show Adani Mining donated $49,500 to the Australian Liberal Party in the 2013-14 financial year, and $11,000 to the Australian Labor Party.

Concerns also emerged before the poll that Adani had inflated the number of jobs its developments were projected to create, with research by the Australia Institute finding the figure had been exaggerated by as much as 300 per cent.

In addition to hundreds of millions promised for multi-use rail infrastructure, Queensland's Newman government had signalled taxpayers could also foot the bill for a plan to dump dredge spoil from mining activities at Abbot Point.

Seeney was the proponent for the plan put to federal Environment Minister Greg Hunt to dump spoil on the nearby Caley Valley Wetlands and said supporting rail infrastructure could start projects in the basin, creating 27,000 jobs for Queenslanders.

In addition to Adani, Gina Rinehart and Indian firm GVK and Clive Palmer's Waratah Coal have projects proposed in the basin area.

Palaszczuk said this week as well as ending taxpayer support for the Galilee Basin, Labor would not dump dredge spoil on the wetlands.

The party has said any projects in the basin must stack up commercially on their own.

However, an alternative location for the spoil has been elusive, given the Labor and Liberal parties have both declared an end to dumping dredge spoil at sea.

Independent Queensland MP Peter Wellington said on Thursday he would support Labor in a minority government, which he said was "conditional on the basis that there is no illegal activity, no allegations of corruption, but, more importantly, it's about providing stability to govern Queensland".

During the previous term of government, Mr Wellington had been critical of the incentives being offered to support Galilee Basin projects.

But Rob Katter disagreed, saying there was justification for building a government-funded rail line if it created jobs. He said funding for the Galilee Basin should be prioritised over $5 billion for a bus and train tunnel in Brisbane.

"We're willing to put Queensland taxpayers' dollars into that but not a rail line that will create jobs and royalties – how does anyone justify that?" he said.

"The only barrier is political ideology that says governments shouldn't be building projects that will be run by the private sector."