The CIA's security procedures at a House subcommittee hearing last week have touched off a sharp exchange of letters between CIA Director William J. Casey and Rep. Benjamin S. Rosenthal (D-N.Y.), the subcommittee chairman.

Casey took exception to the account by subcommittee lawyers who said that CIA officers sought to take the official House reporter and his stenotapes off to Langley after the May 6 closed-door session to supervise preparation of the official transcript.

The CIA director protested in a May 7 letter that no one had proposed taking the House reporter himself to CIA headquarters. Casey assailed as "particularly offensive" a statement by one subcommittee staffer that the stenographer "would have been whisked away to Langley."

In a May 10 reply, Rosenthal said "there may have been a misunderstanding" on that score, but said Casey was overlooking "what I view as the central issue . . . namely, whether the Central Intelligence Agency or the House of Representatives should have control over the conduct of and transcripts from official meetings of House committees involving matters of interest to the CIA."

The hearing by the Government Operations subcommittee on monetary affairs dealt with a House resolution that Rosenthal is sponsoring to authorize disclosure of 17 CIA reports and studies concerning the extent of Arab investments in the United States. Most of the reports are classified "Secret" and some "Confidential."

Casey insisted that the CIA officers at the hearing were simply following "customary and long-established procedure for dealing with classified stenographic notes from closed hearings."

That procedure, he said, is for CIA security officers to "accompany the stenographic materials from the hearing room to the stenographer's working area to convert them into a transcript. If the stenographer plans to produce the transcript at a later time, our security officers store the material in a secure area at CIA headquarters. Thereafter, at any time when the House stenographer is ready to convert the stenographic materials into a transcript, our security officers take the material to him."

Casey complained of what he called the "strident attack" of subcommittee staffers who were quoted in The Washington Post May 7 and said he was writing Rosenthal "lest the American people be misled into thinking that CIA has misbehaved . . . "

A contingent of CIA officers appeared at the session to argue for continued secrecy for the agency's studies. But before it started, Rosenthal said, "CIA security personnel 'swept' the meeting room" and stationed men in the back with special equipment designed to detect radio-type transmissions of the proceedings.

"When the subcommittee staff arrived at the hearing room at 10 a.m. the scheduled time of the subcommittee meeting , the door was locked and guarded by CIA security personnel," Rosenthal protested. "

In any case, Rosenthal said, "only House police officers, not CIA security personnel, have jurisdiction over the grounds and buildings of the House of Representatives."

After the session, Rosenthal said, subcommittee staffers arrived back at their own offices to find "at least eight CIA employes" along with the House reporter. The CIA already had custody of the reporter's tapes and notes, and, Rosenthal said, the reporter stated several times "that he was going with the CIA employes to transcribe the notes. Moreover, a CIA official told a subcommittee staff member that the notes would be transcribed in Langley . . . "

After some apparently vigorous discussion, a CIA contingent escorted the House reporter, Robert Cantor, to his offices and watched over the typing of the transcriptthere, and escorted it back to the subcommittee's offices.

All in all, Rosenthal charged, the CIA's actions show "a lack of sensitivity to the constitutional doctrine of 'separation of powers."

Casey had said the official reporter told the subcommittee staff "on the spot that what we were doing was the normal procedure." Rosenthal voiced some doubt about what was normal procedure, but in any event, he said, the CIA should not have assumed his committee "operated in this fashion" simply because other committees may have done so.