General Motors said it has extended the tenure of its top lawyer, whose department was criticized over how it handled the issue of the automaker's defective ignition switch linked to more than 50 deaths, and the search for a replacement is ongoing. Michael Millikin, 66, will now retire in July and be "available for consulting services" through the end of the year, according to a footnote in the Detroit company's quarterly financial report filed last week with the U.S. Securities and Exchange Commission.