WASHINGTON — The chairman of the Securities and Exchange Commission, a longtime proponent of deregulation, acknowledged on Friday that failures in a voluntary supervision program for Wall Street’s largest investment banks had contributed to the global financial crisis, and he abruptly shut the program down.

Mr. Cox and other regulators, including Ben S. Bernanke, the Federal Reserve chairman, and Henry M. Paulson Jr., the Treasury secretary, have acknowledged general regulatory failures over the last year. Mr. Cox’s statement on Friday, however, went beyond that by blaming a specific program for the financial crisis — and then ending it.

On one level, the commission’s decision to end the regulatory program was somewhat academic, because the five biggest independent Wall Street firms have all disappeared.