Retiring FBI Director Clarence M. Kelley said yesterday that his agents have lost some of their aggressiveness in pursuing criminals because of a fear they might someday be sued because of their actions.

"I think there has been some slowing down of the aggressive attitude that is so necessary in law enforcement," he told a breakfast meeting of reporters.

"You need an aggressive attitude," he said. "Not in the sense of pushing people around, of course . . . But in this present-day atmosphere there is some fear . . . An agent may ask 'Why should I break my neck to pursue this case when I could be sued?'"

Kelley, whose retirement has been delayed until Feb. 15 while a search for a successor goes on, said, however, that he didn't think this "subtle" change in attitude had hurt the FBI's efforts in apprehending criminals.

The civil, suits Kelley referred to number more than 200. "People are just suing now more than they used to," an FBI spokesman explained later.

Some of the suits have been filed by persons targeted by the FBI's programs of break-ins, wiretaps and mail-openings. Kelley said the resolution of the criminal investigation of those so-called "black-bag" operations also has been a matter of concern to agents.

One FBI official, former New York supervisor John J. Kearney, has been indicted in connection with that campaign against radical fugitives in the early 1970s.

Attorney General Griftin B. Bell was forced to reorganize the Justice Department investigation of the black-bag jobs last week when five attorneys quit the case after apparently becoming convinced he would not press for further prosecutions.

Kelley said yesterday, as he has before, that he'd like to see the matter dropped. "There was no corruption involved. It was another era. I'd say Forget about them (such cases) and let's go ahead.'"

He did say that he didn't think "national security" was a consideration in the Kearney case. "That was domestic," he said. Kearney's attorney. Edward Bennett Williams, has asked the government for massive documentation, in an apparent search for evidence to justify Kearney's alleged actions on the grounds the targeted fugitives were backed by a foreign power.

Kelley's 4 1/2-year tenure at the FBI has been marked by turmoils such as the "black-bag" controversy. In his relaxed appearance yesterday, he said he had gradually tried to change the leadership of the bureau, which had become almost a personal fiefdom for long time director J. Edgar Hoover.

"I tried to minimize the position of director to where it would be a coordinator rather than a dictator or an authoritarian figure," he said.

He said he gave Hoover "high marks" for building the reputation of the FBI. But he added, "He was there too long. He established a dynasty and it's not a place for royalty."

Kelley said that at the end of Hoover's service, the director was isolated from what was going on around him.

On other topics, Kelley said he was concerned that the Freedom of Information Act might be used by criminal elements to identify FBI informants.

And he said that he personally would support a law banning cheap handguns known as "Saturday night specials." However, he said he would not favor registration of firearms.