THREE YEARS AGO, President Reagan signed an executive order revising the procedures used in the executive branch to classify national security information. "(I)t is essential," he said, "that the public be informed concerning the activities of its government, but . . . the interests of the United States and its citizens require that certain information concerning the national defense and foreign relations be protected against unauthorized disclosure." Changes in procedures made at that time gave an early indication that in balancing the public's right to know against the government's claims for secrecy, the latter would carry more weight.

Last week, the Information Security Oversight Office in the General Services Administration, the office that oversees classification procedures throughout the executive branch, issued its annual report. It makes dismal reading. Of the four agencies (Defense, CIA, State, Justice) that account for almost all the material that is classified, only the Justice Department reported a reduction in classifications.

The report points out that while the total amount of material classified has risen steadily since the Carter administration, most decisions concerned "derivative material" -- documents containing information already protected by an earlier classification. Original decisions to mark new material secret have risen less dramatically. The oversight office further maintains that classifications in the defense area have increased because more is being done there under this administration. But the trend toward keeping more information from the public is unmistakable.

The work of declassification of old documents has also slowed, though the 1984 figures reflected an improvement over the previous year. Agencies are supposed to mark portions of materials that should be kept secret, rather than stamping whole documents, and to designate automatic declassification dates whenever possible. Few agencies follow these procedures as well as they should.

The report concedes that "overclassification remains a problem." The office singles out for concern a phenomenon it calls "prestige classification": "when the director of a program with national security implications decides that the prestige of the program is elevated by classifying all or portions of it." There are all sorts of human reasons -- prestige, power and control, fear of contradiction, timidity -- that can enter into a decision to withhold information. But in a free society, official secrecy must be minimized. The trend to classify more information and reevaluate less is 180 degrees off.