A House subcommittee has uncovered what appears to be the first instance of "reclassification" of old secrets under an executive order President Reagan issued last year.

The "now-you-see-it, now-you-don't" doctrine was invoked last fall by the Drug Enforcement Administration to block the release of a 1975 report entitled "Problems In Slowing the Flow of Cocaine and Heroin From and Through South America."

A 90-page General Accounting Office study found, among other shortcomings, only limited cooperation between the DEA and the CIA in the field of narcotics intelligence, because of jealousies between the two agencies, differing objectives and finally "a mutual lack of trust."

For instance, the report said, "DEA agents throughout South America stated that CIA intelligence is of little or no value, while CIA officers claimed that their intelligence efforts had resulted in a number of important arrests and/or seizures, and that DEA has failed to follow up effectively in some instances."

The study, classified "Confidential" in the name of national security, was designated for automatic declassification on May 15, 1980. But apparently no one bothered to ask for a copy until a law professor from Florida submitted a request last year.

Acting DEA Administrator Francis L. (Bud) Mullen Jr. "reclassified" the report last Nov. 2. The GAO dutifully notified congressional recipients a month later that the report was being kept under wraps.

Rep. Glenn English (D-Okla.), chairman of the House Government Operations subcommittee on government information, expressed his concern to the Information Security Oversight Office (ISOO). He said staff members familiar with drug enforcement policy had reviewed the report and concluded there was "no apparent reason for its continued classification."

"The apparent lack of sensitivity of the information in the 1975 report, combined with the two-year gap in classification gives rise to suspicion that the reclassification may have been more to prevent embarrassment on the part of the drug enforcement bureaucracy than to protect information in the interests of national defense or foreign policy," English said. He noted that the GAO was working on another report critical of the DEA's drug enforcement efforts.

At the prodding of ISOO Director Steven Garfinkel, the DEA removed the national-security label and agreed last Friday to make the report public.

"To suggest that the delay had anything to do with the fear of embarrassment to the agency is ridiculous, a fact well known to congressmen who were interested in the issue," DEA spokesman Robert Feldkamp said this week.

Spokesmen for English and Garfinkel both said that, as far as they knew, it was the first time a document had been reclassified under the Reagan executive order. The April 2, 1982, order, which greatly expanded the scope of government secrecy, allows officials to "reclassify information previously declassified and disclosed" if it can "reasonably be recovered," and they also can "reclassify" information that is declassified but has yet to be disclosed after receiving a request for it.

The GAO report also said that the DEA had stopped sharing enough information to help Customs Service drug-interdiction efforts at U.S. ports. As for CIA-DEA relations, the study said that much of the CIA's intelligence in the narcotics field "comes from highly paid informers that have been cultivated and groomed over many years" and that the CIA "takes every precaution to protect" them from DEA enforcement efforts.

In turn, the study said, "it is not uncommon for DEA agents to refer to the CIA as the 'spooks' or to express amazement at how such a large organization can operate without any outward signs, such as arrests or seizures, to justify their existence."