A regional inspector general for the embattled Environmental Protection Agency has written a memo instructing his staff not to get caught "with our pants down" by releasing information about the agency's activities to Congress or the public.

The memo from James J. Conn Jr., divisional inspector general of EPA's mid-Atlantic division, advises his subordinates to go to great lengths to destroy and conceal information "which could prove embarrassing" if made public, even to members of Congress. Conn said the orders came from "AIG-I," presumably the agency's inspector general, Matthew Novick.

As soon as investigators complete a case "we have to start thinking about what to get rid of before an FOIA Freedom of Information Act request catches us with our pants down," Conn said in the Aug. 27 memo.

But he says that even this rule isn't foolproof because the public, under the act, is entitled to some potentially embarrassing information before cases are resolved.

So other measures must be considered, Conn adds. "We can no longer duck materials in our desk and private workpaper files and hope to exempt them from disclosure."

The memo, obtained by Rep. James H. Scheuer (D-N.Y.), is a study in bureaucratic evasion tactics. That is clear even from its title: "Talking Paper on How and When to Purge Divisional Case Files of Material Which Could Prove Embarrassing if Released Under an FOIA or Congressional Request."

The problem, it seems, is that Conn's office has been "caught with its pants down" before. The most recent case involved Hugh Kaufman, a special assistant to Rita M. Lavelle, assistant administrator for solid waste and emergency response.

Kaufman is a well-known whistle blower, who frequently uses his nongovernmental time to advise citizens on how to mount campaigns to correct environmental problems in their area.

Last summer, Kaufman visited a group in western Pennsylvania on such a mission. Before he left Washington, he filled out a form, checking a box that said he was taking sick leave. Someone spotted this, and an investigator was flown out to observe him.

The investigator, according to Scheuer aides, came back thinking he had the goods on Kaufman. He had pictures of him talking to a citizens group, entering a motel room that night with a woman and coming out with her the next morning.

The case quickly fell apart, however. Kaufman said he had checked the wrong box on the form, and that he had meant to take annual leave, making the trip perfectly legitimate. The woman, futhermore, was his wife.

The real reason for the investigation became clear when Kaufman filed an FOIA and got hold of instructions given to the investigator before he left on his trip.

"Rita Lavelle wants him fired," the instructions said.

Conn's memo was apparently an attempt to prevent similar memos from falling into the wrong hands. He admits, "I am at a slight loss in trying to come up with a set of rules" for this," and he asks for advice from his staff.

The memo fell into the hands of Scheuer, chairman of the House Science and Technology subcommittee on natural resources, agriculture research and environment. He was so outraged at what he called the "distasteful implications" of the memo that he fired off a letter to President Reagan.

"Mr. President, this memorandum, in my judgment, skirts perilously close to advocating subversion of applicable statutes under which the inspector general operate," he wrote.