The bitterness with which some veteran FBI agents view the Justice Department attorneys investigating the FBI break-in cases has come to light in a unique federal court suit.

In the suit U.S. District Court in Alexandria, a longtime FBI official charges the department lawyers with unethical, improper and possibly illegal" actions in their pursuit of the break-in inquiry.

The suit by the 25-year FBI veteran is not without ironies. A career intelligence office, Ryan's job often has been to prevent outsiders from getting information about the FBI. Now he is invoking the Freedom of Information Act.

A department spokesman said his suit is the first instance of a current Justice employee going to court to gain access to departmental documents.

In letters filed with the suit, Ryan charges that J.Stanley Pottinger, the former Civil Rights Division chief who once headed the break-investigation, improperly had him "insulated" last summer from other FBI agents who were targets of the inquiry.

He said Pottinger's July 9, 1976, request led to his being prevented from investigating news "leaks" about the investigation and reporting that a Civil Rights Division attorney had gained unauthorized access to FBI documents by making a false certification.

A department spokesman said the allegations are under review.

A former FBI supervisor in New York City, John J.Kearney, was indicted in April on charges of directing a mail-opening and wiretapping operation against radical fugitives in the early 1970s.

His has been the only indictment so far from an extensive inquiry into the FBI's use of burglaries and other surveillance on political militants.

A federal grand jury in Washington is still hearing testimony in the case.

In his suit, Ryan contends, in effect that the investigators took improper shortcuts in pursuit of their FBI targets. Ryan, in turn, apparently was one intent on obstructing the investigation.

Ryan served for a time with the New York office and knows several of the agents under investigation, accorking to sources familiar with his career. His duty in New York was in the 1960s, before the break-ins began.

According to letters attached to the suit, Ryan's attack on the Civil Rights Division attorneys began in January. It was then that he first requested a copy of the July 9, 1976, memo from Pottinger to FBI Director Clarence M.Kelley which he said asked that Ryan be reassigned and "insulated" from others agents.

After several more letters and appeals, Deputy Attorney General Peter F.Flaherty, on May 26, released the July 9 memo to Ryan.

In that memo, a copy of which is attached to the suit, Pottinger adked specifically that Ryan be removed immediately from any contacts with the investigation.

"His insulation from this case should include not only contacts with any agents under investigation but any classification of documents or materials pertaining to matters under investigation," Pottinger wrote.

He also referred to conversations Ryan had been having with Horace Beckwith, an agent who followed Kearny as FBI supervisor in New York City.

Sources familiar with circumstances of that reference said Ryan had been talk to his attorney about the case until the lawyer had the proper clearance.

Other sources claimed that Ryan continued to insist that Beckwith not discuss classified information, even after his attorney had received proper clearance.

Pottinger said in the memo he was asking that no one in the bureau discuss the investigation with those agents who were targets because it might inhibit their willingness to cooperate.

Pottinger, now an attorney in private practice in Washington, declined comment except to say, "It seems curious that the Justice Department is releasing internal documents about continuing investigation."

Ryan also declined comment.

In releasing the July 9 memo, to Pottinger from William Gardner, the day before, could not be disclosed because it contained information about the pending break-in investigation.

Quinlan J.Shea Jr., who reviewed both documents for Flaherty, characterized the July 8 memo as saying Ryan was "getting in the way" of the invesgators.

Similarly, Ryan's %false certification" charge against a civil rights attorney is said to refer to an instance where investigators swore they had proper clearances to inspect FBI documents. Ryan has also chargedthat Pottinger refused to let him investigate the source of one news "leak" about the investigation.