New York regulators have sued American International Group Inc., accusing the nation’s largest insurance company and two former top executives of orchestrating an accounting scheme to boost the company’s stock price.

The civil lawsuit, filed Thursday, accuses AIG’s former chief executive and chairman, Maurice “Hank” Greenberg, and chief financial officer, Howard I. Smith, of using “deception and fraud” to make the company’s financial picture appear brighter than it was, misleading both investors and state regulators.