WASHINGTON — The official in charge of Medicare and Medicaid for the last 17 months says that 20 percent to 30 percent of health spending is “waste” that yields no benefit to patients, and that some of the needless spending is a result of onerous, archaic regulations enforced by his agency.

The official, Dr. Donald M. Berwick, listed five reasons for what he described as the “extremely high level of waste.” They are overtreatment of patients, the failure to coordinate care, the administrative complexity of the health care system, burdensome rules and fraud.

“Much is done that does not help patients at all,” Dr. Berwick said, “and many physicians know it.”

In an interview on Thursday, his last day on the job, Dr. Berwick reflected on his successes, failures and frustrations in trying to engineer a rapid transformation of the health care system while beating back criticism from Republicans in Congress.

President Obama nominated Dr. Berwick to be the administrator of the Centers for Medicare and Medicaid Services in April 2010. While the Senate was investigating his qualifications, Mr. Obama circumvented Congress by giving Dr. Berwick a temporary recess appointment, a shortcut that infuriated Republicans and irked some Democrats. The appointment was due to expire at the end of this year.