Indian conglomerate GVK Group's $10 billion Alpha coal project in Australia's Galilee Basin is uneconomical, a report by the Institute of Energy Economic and Financial Analysis says.

The institute, based in Cleveland, described Alpha as "stranded in the valley of death."

The Alpha project includes the development of the largest black coal mine in Australia, a 308-mile long railway line and new coal export terminal in the Great Barrier Reef World Heritage area.

Already approved by both the federal and Queensland governments, Alpha is expected to produce about 32 million tons of coal a year from an opencut operation over 30 years.

GVK paid Australia's Hancock Group $1.26 billion for the Alpha deposit in September 2011. At that time, the price for thermal coal was near its peak at $133 a ton.

But coal prices have fallen about 30 percent in the past 18 months and mining giants such as BHP Billiton and Rio Tinto have signaled that they may sell some of their coal assets.

IEEFA's report says that GVK would need a sustained thermal coal price far in excess of the current spot rates of $88 ton from Newcastle, Australia.

"Coal markets are weak now, and a strong, sustained comeback is less likely in the face of the maturation of renewable energy, the changing nature of growth in many countries and public concern over coal's health and environmental impacts," report co-author Tom Sanzillo, a former first deputy comptroller of New York State, was quoted as saying by Mining Weekly Online.

The report says in addition to being highly over leveraged, GVK carries a debt of $2.8 billion with a market capitalization of only $243 million, and faces a plummeting stock price, which has underperformed the Indian share price index by 80 percent since 2010.

In a statement to Mining Weekly, GVK questioned the validity of the IEEFA report, noting it was commissioned, sponsored, and funded by Greenpeace, which the company said is sponsoring a media campaign "to discredit the use of coal and to curtail the growth and development in mining, transport and other sectors where infrastructure/construction is required."

The timing of such a campaign, GVK said, "is to create hurdles when GVK is seeking [and is confident of getting] clearance for dredging in about a month's time."

"We remain extremely confident of the successful, responsible delivery of our projects with our proven, experienced Australian management team," GVK's statement said.