The FBI is still conducting its own investigations of "any new leads and new evidence" in the murders of President Kennedy and the Rev. Martin Luther King, Jr., the House Assassinations Committee was told yesterday.

Lawyers for the House committee did not elaborate on the FBI's justification for its continuing detective work, but several committee sources privately expressed chargrin about it, especially in light of widespread criticism of the bureau's original handling of the cases.

Last year, the Senate intelligence committee concluded that the FBI and the Central Intelligence Agency had concealed crucial information during the course of investigating President Kennedy's assassination.

House committee Chairman Louis Stokes (D-Ohio) wondered at a hearing of his panel yesterday morning whether it would be safe to conclude that "as far as the FBI is concerned, both investigations are still open."

Deputy counsel Stephen J. Fallis did not answer directly, but said he had been assured by Justice Department and FBI officials "that they are not conducting a full, complete or de novo investigation" of either assassination.

Fallis said the officials told him "they are only interested in pursuing any new leads and new evidence that comes to their attention and coordinating" their efforts with the House committee.

He said the FBI had promised to "give us virtually immediate notification of the areas they are investigating in these two assassinations." Fallis said he hoped this would keep the committee, the Justice Department and the FBI "from stepping on each other's toes.'

In response to a follow-up inquiry, a Justice Department spokesman denied to a reporter that the FBI was trying to head off any embarrassments that might result from discoveries by House investigators during the next year and a half.

Although neither the Kennedy nor King assassination was a federal crime, the spokesman said the FBI was continuing to investigate new leads under the federal law prohibiting conspiracies to deprive anyone of his civil rights.

"They'd be derelict if they didn't" continue to investigate, the spokesman insisted, adding that the five-year statute of limitations would not apply "if a conspiracy is still going on."

In addition to the putative competition from the FBI, the House committee was confronted yesterday with reports of an incipient lack of cooperation from the Senate Intelligence Committee now headed by Sen. Daniel K. Inouye (D-Hawaii).

Stokes said that part of the problem was that committee staffers are still awaiting security clearances from the FBI and the CIA, but House committee lawyers indicated they have gotten very little response to the "substantial requests" they have made for Senate committee records bearing on the assassinations.

Rep. Stewart B. McKinney (R-Conn.) said he hoped the Senate committee would recognize that "we work for the same government," and urged Stokes to start applying "vise-like" pressures if cooperation is not forthcoming.

Inouye said later, through a spokesman, that he had received "one official request from the assassinations committee and I have responded to it." The spokesman declined to elaborate on Inouye's response, but it apparently was not a substantive one.