Mary Barra, General Motors’ new chief executive officer, was in a tough spot recently as she tried to explain to Congress why her company didn’t quickly recall cars it knew contained defective and clearly dangerous parts.

The choices appeared to be that GM was either corrupt or incompetent. Instead of selecting one of those, Barra chose to plead ignorance.

It was not a popular choice. As a consequence, the latest denizen of GM’s corner office got to experience congressional anger at its highest pitch — which is what happens when news cameras are rolling.

California Sen. Barbara Boxer was a leader of the outraged as she peppered Barra with questions.

“You don’t know anything about anything,” Boxer said at one point.

Barra tried to assure the senators that GM is now focused on safety and the consumer, but Boxer was not assuaged.

“If this is the new GM leadership, it’s pretty lacking,” she fumed.

Two other senators, both former prosecutors, raised the specter of criminal prosecution.

“I don’t see this as anything but criminal,” said Sen. Kelly Ayotte, R-N.H.

Sen. Richard Blumenthal, D-Conn., said the more he learns about GM, “the more convinced I am that GM has a real exposure to criminal liability.”

Barra’s main accomplishment of the day was substantial: She inspired bipartisan concurrence. But it probably wasn’t exactly what she had in mind.

We’re with Blumenthal: The more we learn, the more outrageous GM’s actions appear.

It’s increasingly clear that GM covered up information about defective ignition switches in at least two of its vehicles — Chevrolet Cobalts and Saturn Ions — and that those defects are linked to 13 deaths and dozens of accidents.

Earlier in the week, Barra apologized for the company’s actions during a tear-filled meeting with families who had lost loved ones from these crashes. Then she appeared before a House committee, where she again apologized and promised that many of the answers Congress seeks will be found in an internal GM investigation that should be completed in 45 to 60 days.

She apologized a third time at the beginning of the Senate subcommittee hearing, but it was wearing thin.

Barra’s strategy is to rely heavily on the results of that internal investigation. But if it’s going to help, it better be finished in less than two months, and it better be a good one. A really good one.

A substandard investigation is sure to earn Barra an “invitation” back to the Senate subcommittee. And next time, they won’t be so nice.