WASHINGTON — Lawmakers on Thursday demanded General Motors fire its chief lawyer and open its compensation plan to more potential victims as a Senate subcommittee delved deeper into GM’s mishandling of the recall of small cars with defective ignition switches.

Sen. Claire McCaskill, D-Mo., who chairs the subcommittee, praised GM CEO Mary Barra, saying she “has stepped up, and with courage and conviction has confronted the problem head on and the corporate culture that caused it.”

But McCaskill also put Barra on the spot, telling the CEO that she should have fired GM’s corporate counsel, Michael Millikin, based on the conclusions of an internal report by outside attorney Anton Valukas. Millikin sat next to Barra as she defended him as a man of “tremendously high integrity.”

The Valukas report found that GM’s legal staff acted too slowly to share details of settlements it was making in cases involving Chevrolet Cobalts and Saturn Ions where the front air bag hadn’t deployed in a crash. The lawyers didn’t alert engineers or top executives to a potential safety issue.

McCaskill also questioned why Millikin didn’t inform GM’s board or the U.S. Securities and Exchange Commission of the potential for punitive damages as GM settled the cases, saying, “This is either gross negligence or gross incompetence on the part of a lawyer,” she said.

Millikin said he only learned about the ignition switch problems in February and acted quickly once he did. He said any potential settlement must now be brought to him before any action is taken.

But Sen. Richard Blumenthal, D-Conn., also called for Millikin to be fired, saying that an ongoing Justice Department investigation will likely find evidence of “cover-up, concealment, deceit and even fraud” within GM’s legal team.