General Motors Co. and plaintiffs lawyers are fighting over the scope of the upcoming deposition of the lawyer whose report on the company’s ignition-switch defect blamed a handful of employees for the fiasco.

Jenner & Block chairman Anton Valukas issued the 315-page report last year explaining how GM failed for more than a decade to identify a defect that causes the ignition switch to slip into the accessory position, shutting down engines and disabling airbags.The defect prompted recalls of 2.6 million cars and trucks worldwide and has been linked to 124 deaths.