The documents were filed with the Nova Scotia Utility and Review Board, which begins hearings on the multibillion-dollar venture next month.
The NDP government said new information submitted by consultant John Dalton showed the cost of building a subsea link between Nova Scotia and Newfoundland would be cheaper than two alternatives not considered in a report he released in January.
But the Liberals say a consultant's report done for the province's consumer advocate showed that a separate analysis by Emera (TSX:EMA) is faulty and biased to favour the utility company's desired outcome.
Liberal Energy critic Andrew Younger called the advocate's report "damning" because it was done by what he contends is the only truly independent entity in the regulatory process.
"They are saying the government got it wrong, Nova Scotia Power got it wrong and that they are torquing this process in order to get the result they want," said Younger.
The report is by Levitan & Associates, Inc., a Boston-based energy management consulting firm specializing in the natural gas and electricity markets.
The consultants dispute Emera's assertion that the Maritime Link represents the lowest cost alternative.
But Premier Darrell Dexter said a series of other reports, including the one done by Dalton, demonstrate the benefits to Nova Scotia ratepayers and it will be up to the review board to decide who's right.
He said his confidence in the project has not been shaken.
"Not at all," said Dexter. "What I'm even more confident in is that there are so many expert reports coming forward that support the Maritime Link."
Dalton's submission said the link would cost $560 million to $973 million less than acquiring energy from Hydro Quebec using 300 megawatts of transmission capacity through New Brunswick. He also contended it would be $1.5 billion to $1.77 billion cheaper than opting for a natural gas alternative.
In January, he said buying power from Muskrat Falls would be $402 million cheaper than importing it from Quebec and would be $1.5 billion less than using a mix of wind and natural gas over the 35-year life of the commercial contract for the hydroelectric development.
Proponents of the $7.7-billion hydro development in Labrador hope it begins generating power by 2017.