ST. JOHN'S, N.L. -- Former premier Danny Williams told the Muskrat Falls inquiry on Monday that the wildly overbudget megaproject was in Newfoundland and Labrador's best interest -- and critics who attack him for championing it are "reckless."

Williams maintained "good intentions and good faith" were behind the planning of the hydroelectric dam that has doubled its estimated cost, leaving the province's ratepayers worried the endeavour might be paid out of their pockets.

"This is something we can be really proud of," the boisterous former Tory premier said of the Labrador project.

"The fact that the project is getting disparaged reflects on all the people who worked so hard in order to put this together."

The independent inquiry, led by provincial Supreme Court Justice Richard LeBlanc, is looking into cost and schedule overruns of the $12.7-billion dam on the lower Churchill River.

The 824-megawatt hydroelectric dam, being developed by the Crown-owned Nalcor Energy, will send power to Newfoundland and later Nova Scotia through subsea cables.

During his term, Williams championed Muskrat Falls as a form of energy independence from Quebec, before retiring from politics shortly after announcing the plan in 2010.

The dam near Happy Valley-Goose Bay has since been described as "the greatest fiscal mistake in Newfoundland and Labrador's history" by current Liberal Premier Dwight Ball.

Williams, a businessman and lawyer, was comfortable and confident on the stand on Monday - but he didn't mince words when addressing criticisms from his detractors.

Commission co-counsel Barry Learmonth asked Williams to respond to criticisms that he pushed the megaproject through for the sake of his own ego and legacy.

Williams called such criticisms "reckless, irresponsible and shameful."

"Nothing, I'm under oath, could be further from the truth," said Williams.

Williams maintained that his government "turned over every stone" by researching financial and legal options before his successor as Tory leader and premier, Kathy Dunderdale, sanctioned Muskrat Falls in December 2012.

Williams also praised a paper that historian Jason Churchill presented to the inquiry last month. It found that Quebec's stronghold on the Churchill River's resources has long blocked Newfoundland and Labrador from accessing elusive energy markets.

Williams detailed his own frustrations with Quebec, including the long-standing debate over Labrador's borders -- which, according to commission exhibits, are not reflected in some Quebec maps.

Williams also referred to former premier Jean Lesage's 1965 comments that any electricity passing through Quebec territory would "become property of Hydro-Quebec."

"They will do whatever they can to cut us off, it's shocking," Williams said. "(But) I need to point out that we still tried."

Learmonth asked Williams about testimony from megaproject scholar Bent Flyvbjerg, who said last month there can be an increased risk of cost overruns when those overseeing the project have less experience in hydroelectric projects.

But Williams said he was "not at all concerned" the Nalcor Energy team was underqualified to oversee a hydroelectric project, despite mainly being experts in oil and gas projects.

He said he had no reason to believe Nalcor staff had misrepresented cost estimates in communications with him.

Williams also dismissed the "rumours" that he continued to influence Muskrat Falls management decisions after he resigned as premier in 2010, attributing such comments to "Danny haters."

"The day I went out the door, I was done," said Williams. "Whoever is putting that out there is putting it out there for the wrong reasons."

Williams said concerns over doubled power rates are the result of "fear-mongering," and the project's long-term benefits will outweigh rate increases that Williams said were on the horizon anyway.

"Critics can't throw all of this on the back of Muskrat Falls," said Williams. "I can guarantee the people of this province that these rates will not double as a result of Muskrat Falls."

The former premier said Nalcor will become more profitable over time, and its profits will help mitigate the costs.

"There was never an understanding that we would get this for free," Williams said of Muskrat Falls.

Williams will continue his testimony Tuesday.