Manitoba Hydro's head office is based in a recently-constructed downtown Winnipeg building. (CBC)

A Manitoba Hydro whistleblower said Tuesday that employees at the publicly owned utility are being threatened to stay quiet about allegations of mismanagement and that she fears an investigation into her claims is being swept under the rug.

The whistleblower is a former Hydro consultant who works for a New York-based risk-management firm. She came forward nearly a year ago to allege that the Crown corporation is miscalculating how much power it can generate and sell and that the province could face significant blackouts in the future.

A complaint filed with the Manitoba Ombudsman's Office under provincial whistleblower legislation in December 2008 accuses the utility of taking too many risks with the province's power supply and alleges mismanagement has cost Hydro more than $1 billion.

The complaint also suggests Hydro CEO Bob Brennan was told that future financial forecasts are incorrect. When he was supplied with evidence of that he ignored it, the complaint alleges.

CBC News has decided not to identify the whistleblower at her request.

Hydro CEO Bob Brennan has denied the consultant's allegations, saying previously that they were "flawed," and that a blackout "just couldn't happen."

In an internal memo dated Oct. 26, Brennan told Hydro staff that the reports of potential blackouts and financial difficulties "are completely misguided and without any substance whatsoever." He also called the allegations of mismanagement "hurtful."

But the whistleblower said in a Tuesday interview with a CBC News investigative team that Brennan is relying on calculations from an archaic computer system to make that statement.

In an open letter obtained by CBC News, the whistleblower said what she uncovered were "'systemic and massive' computer system flaws — with obsolete computers maintaining the calculations.

"Massive system errors and inadequate mathematics were found in the power calculation of 'blackouts' or reliability conditions — which could lead to faulty results in keeping the lights on," the letter said.

She also said she has sources within Hydro that are being told they'll be fired if they continue to talk and that some are already being subjected to internal investigations.

"People should not be in a position of having their livelihoods threatened to participate in an important investigation of serious allegations," she said. "It's a way of trying to prevent the facts from coming out."

She added that she's never been asked by the provincial auditor to produce her evidence.

A Hydro spokesman said Tuesday that no employees have been threatened with dismissal. Neither have any come forward to file allegations similar to the whistleblower's, he said .

Auditor general admits to slow response

On Oct. 21, Manitoba Finance Minister Rosann Wowchuk announced a special audit of Hydro based on the whistleblower's complaint and asked the Office of the Auditor General to make it a priority.

Tuesday Auditor General Carol Bellringer said her office has not yet received all of the documentation needed to complete the probe and admits it should have been tackled more quickly.

In his memo to staff, Brennan also said he's confident the auditor's review "will vindicate Manitoba Hydro and demonstrate that the corporation is managing its risks in the most prudent and responsible manner."

CBC News has made available the consultant's letter and Brennan's internal memo to online readers.

They can be found by clicking the links at the right near the top of this story.

If you have any tips for the CBC News investigative team, call the confidential tip line at 204-788-3744.