ST. JOHN'S, N.L. - A new report by Newfoundland and Labrador's Public Utilities Board says it lacks the information it needs to assess whether the proposed Muskrat Falls hydroelectric project is the cheapest energy option.

The board says information provided by Nalcor Energy, the province's Crown energy corporation, was not detailed enough to conclude whether Muskrat Falls should proceed.

Nalcor and Nova Scotia's private utility Emera (TSX:EMA) are working on a deal to jointly fund the $6.2-billion project.

Muskrat Falls would bring power from Labrador to Newfoundland and then Nova Scotia using subsea cables.

The Newfoundland and Labrador government asked the utilities board to assess whether the power is needed and if Muskrat Falls is the cheapest option before it sanctions the project.

The board had asked for an extension beyond March 31 for its review but the provincial government refused.

In its report released Monday, the board refers to "gaps in Nalcor's information and analysis," noting that electrical integration studies were not done, nor were industry-standard reliability studies.

The board also cites "uncertainty" surrounding the project's adherence to standards set by the North American Electric Reliability Corporation, and it says the design of a key overland transmission line "is not in accordance with accepted standards and best practice."

"Of particular concern to the board is the fact that Nalcor does not accept the recommendation of MHI (Manitoba Hydro International) with respect to transmission line design criteria," says the board, referring to a separate Muskrat Falls review released in February.

Such gaps could affect not only "project definition and costs" but also reliability of a crucial power source, says the board.

Any major power loss that may result "could significantly impact Hydro's utility and industrial customers and lead to additional costs for the system and customers, in addition to the possible societal and economic impacts associated with an extended outage."

Conservative Premier Kathy Dunderdale, an avid supporter of Muskrat Falls, was scheduled to respond later Monday.

Nalcor has said it is working to close some of the data gaps described in the Manitoba Hydro International report.

Cheryl Blundon, a spokeswoman for the Public Utilities Board, said the report speaks for itself and there will be no further comment.

The board received its terms of reference last June and was to report by Dec. 30. It was granted one extension for its review but was denied a second one, which meant limiting public hearings to St. John's instead of planned sessions across the province.

Board chairman Andy Wells accused Nalcor of being slow to provide requested information, a process he described as "torturous."

Nalcor countered that it was co-operative and did its best to comply with multiple and complex requests for data.

There were doubts in some quarters about the board's ability to assess the project.

Former Tory premier Brian Peckford wrote an open letter to Dunderdale in February, saying Muskrat Falls should be independently reviewed by international energy experts.

"Frankly, the board and its staff do not have the expertise to evaluate this project," Peckford wrote.

He said the board is primarily a regulatory body tasked to deal with electricity rates and petroleum pricing.

"It is not structured to assess a multibillion-dollar project, examining it against other modes of generation and transmission."

Opposition critics have also cast doubt on the process.

Provincial NDP Leader Lorraine Michael declined a chance to present her views at hearings before the board's commissioners, saying the government is rushing a costly project without doing enough to weigh alternatives.

Dunderdale has shrugged off such criticisms. She says Muskrat Falls has been studied in one form or another for decades. Supporters of the project say Muskrat Falls is the cheapest way to meet the province's growing energy needs.

The review of the project released in February by Manitoba Hydro International found that it's the cheapest energy option, although it warned of risky variables such as construction costs that could drive up the price tag.

And a report last September by global energy analyst Navigant Consulting used Nalcor data to conclude that Muskrat Falls would cost about $2.2 billion less through to 2067 than if Newfoundland stayed disconnected from mainland power sources.

Critics, however, cite concerns about cost overruns. They also quote the findings of a joint federal-provincial environmental review panel that found proof lacking for both the need and viability of the project.

Muskrat Falls has since passed federal and provincial environmental assessments as Ottawa and the province finalize a promised federal loan guarantee.

But a coalition of environmental groups, represented by lawyers for Ecojustice, have filed an application for a judicial review. They say the environmental review was incomplete and should be revisited.