Here's what GM needs to do: Ralph Nader

Consumer advocate Ralph Nader told CNBC on Wednesday he thinks General Motors should hire an independent ombudsman, reporting to CEO Mary Barra, to whom engineers can report problems without fear of retaliation.

"Engineers, who know what the defects are, but are being told to shut up and get in line can complain to [this ombudsman] and they can be covered anonymously," said Nader on "Squawk on the Street." "They can be guaranteed they're not going to lose their job if they report a defect that's being covered up to the company ombudsman."

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Committees in the House and Senate are investigating why it took GM more than a decade to recall 2.6 million cars that could have faulty ignition switches and may have contributed to at least 13 deaths. The largest U.S. automaker also faces a criminal probe by the Department of Justice.

Nader, who gained attention in the mid-1960s for criticizing car companies for a lack of safety features, complained that while Barra said she learned of the defect on Jan. 31, the automaker has yet to conclude what caused the defect because its internal investigation is still underway.

In addition to hiring an ombudsman, Nader thinks its internal investigation would be expedited if GM didn't have so many layers of management that he described as a "huge mass of ambiguity."

"There's not a clear line of responsibility from the design committees to the review committees to the approval of the overall vehicle," Nader said. "This is a gigantic bureaucracy that does not ascribe specific responsibility and accountability at the get go."

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Besides a congressional investigation, General Motors faces a consumer class action lawsuit filed by attorney Adam Levitt on behalf of owners and lessees of GM cars with the defective ignition switches. The total dollar amount in damages has yet to be determined, but Levitt told CNBC it will be "very, very substantial number."

"Every single one of these cars had an inherent defect when it rolled off the factory floor. Every single one of these cars, if the consumers were fully aware or frankly aware at all of this problem at the time they purchased these cars, they either wouldn't have purchased them at all or they would have paid a lot less for them," Levitt said on "Squawk on the Street," adding GM's handling of the recall is "arguably the most serious cover-up in U.S. automotive history."

General Motors declined to comment directly on the suit, but a company spokesperson offered the following statement.

"We don't comment on pending litigation, however we will respond to the complaint in due course. Our focus right now is on getting the vehicles fixed as quickly as we can, minimizing the inconvenience to our customers, and figuring out what went wrong and why. We are also making the changes necessary to ensure that something like this never happens again."

—By CNBC's Drew Sandholm with Reuters. CNBC's Stefanie Kratter contributed to this report.