A. Daniel O'Neal, the new chairman of the Interstate Commerce Commission, has sent President Carter a report highly critical of the way the commission has been run in the past.

The ICC - the nation's oldest regulatory agency - oversees the rail, bus and trucking industries. It has been the subject of at least three major studies in the past 20 years, all of which have urged management reforms that have gone largely ignored. In his report, released this week, O'Neal was unsparing in outlining what still ails the 90-year-old agency.

He called the commission's current management team weak. He said the agency lacks purpose and direction. And he stated that communication between the agency's headquarters and its 79 field offices was poor.

The commission, said O'Neal who served as a member of the board for four years before being appointed chairman by Carter this year, "is burdened by organizational and management problems which include the absence of effective coordination and management of agency resources, the lack of a strong policy planning entity, and communications and structural imbalances."

He criticized the agency for lacking foresight and for taking "a piecemeal approach" to problem solving. The ICC makes about 40,000 decisions each year, he noted.

"The commission, in short, has tended to function as a fragmented system of courts of law rather than as a single administrative agency and has taken narrow, legislatic, judicial approaches to problems which require decision based on sound economics and practical analyses," O'Neal wrote Carter.