Plaintiffs lawyers leading hundreds of lawsuits over General Motors Co.’s ignition-switch defect on Monday defended their management of the multidistrict litigation, which came under attack after the first bellwether trial imploded abruptly last month amid revelations of apparent fraud and perjury.

The three co-lead plaintiffs attorneys, in a response to a motion filed in New York federal court, insisted that they had worked “tooth and nail” on the litigation and that the first bellwether, despite its unraveling, would aid the MDL going forward.