DETROIT — In their most aggressive crackdown yet on auto safety, federal regulators on Sunday levied a record penalty of $105 million against Fiat Chrysler Automobiles for failing to complete 23 safety recalls covering more than 11 million vehicles.

The civil penalty is the largest ever imposed by the National Highway Traffic Safety Administration on an automaker for recall violations, surpassing the $70 million fine imposed in January on Honda for under-reporting hundreds of death and injury claims. .

It also represents an escalation of the agency’s efforts to investigate and punish automakers that do not adequately recall and fix defective models.

“This civil penalty puts manufacturers on notice that the department will act when they do not take their obligations to repair safety defects seriously,” said the secretary of transportation, Anthony Foxx.