Two federal prosecutors and an FBI agent were censured and four other FBI agents were disciplined yesterday as a result of a six-month, $500,000 investigation of Justice Department news leaks.

Not identified, censured or desciplined at all was whoever in the FBI or its parent Justice Department leaked a prosecutive memorandum to The New York Times detailing evidence against four of the six congressmen and one senator charged in the Abscam iinvestigation before the charges were formally filed.

"We do not know who leaked the prosecutive memo that was the basis for some of the first stories on Abscam," Attorney General Benjamin R. Civiletti said yesterday at a news conference. "We're not at all certain who the first leakers were."

The department censured the two chief federal prosecutors in Philadelphia -- U.S. Attorney Peter F. Vaira Jr. and his deputy, John F. Penrose. Vaira was censured for calling a reporter at The Philadelphia Inquirer to alert her that The New York Times had obtained information about Abscam. Penrose was censured for telling reporters at two Philadelphia papers that the Abscam investigation in Philadelphia involved the use of certain fictitious Arab words and an undercover agent using a specified fictitious name.

Also censured was Robert John Barron, an FBI special agent and a supervisor in the Los Angeles office. The investigation found evidence that Barron was the leak to The Los Angeles Times of extensive disclosures in the FBI's Brilab investigation, an operation similar to Abscam that focused on corruption in the labor movement. Barron was censured on the eve of his retirement, in part because "of his lack of candor" and his refusal to take a lie detector test.

Four FBI agents were disciplined -- one who leaked news of Abscam, two of Brilab and a fourth of Pendorf, a criminal investigation of corruption in the gambling casinos of Las Vegas.

Not identified or censured was whoever in the FBI leaked to a television network the news that FBI agents involved in the Abscam investigation would be calling at the home of Sen. Harrison A. Williams (D-N.J.) at a particular time on a particular night. The network filmed the arrival and departure of the agents across the street from Williams' house in Washington. d

"We had evidence that hinted at one or more individuals in the network leak," said Richard Blumenthal, the U.S. attorney for Connecticut who was put in charge of the investigation, "but the evidence was not sufficient to discipline anybody that may have been involved."

Blumenthal said that the investigation of news leaks into the Abscam, Brilab and Pendorf undercover operations involved 30 FBI agents and five Justice lawyers. The agents conducted 1,253 interviews and visited 77 cities to get interviews and sworn statements. Lie detector tests were given to 21 employes at Justice, 18 of whom were asked to take the test and three of whom volunteered for it.

"The investigation cost $500,000," Blumenthal said. Added Civiletti: "This investigation has had results more tangible than any other inquiry of its kind inside the Justice Department."

The highest-ranking official to be disciplined was Assistant FBI Director Oliver B. (Buck) Revell, who received an official letter of censure from FBI Director William Webster and last week was moved out of his post as head of the criminal division to an administrative job. Revell was disciplined for exchanging confidential information for two years about Brilab with an investigative reporter for The Daily Oklahoma.

The harshest discipline was handed out to FBI agents Quentin G. Ertel Jr., of the New York office; Jack D. Blair, a supervisor in the San Diego office, and Cluster Hall Jr., a supervisor in the New Orleans office assigned to the Pendorf investigation in Las Vegas.

Ertel was suspended without pay for 30 days, placed on probation for an unspecified time and reassigned from his press relations job for urging an Abscam investigator to meet with a New York Times reporter. Ertel was also believed to be the source of an article in The New York Times that an Abscam defendant had agreed to cooperate with the FBI. The information Ertel is believed to have passed on to The Times had already appeared in The Washington Post.

Blair was reduced in grade (from GS14 to GS13), removed from his supervisory job and placed on probation for an unspecified time. The action was taken against him "for unauthorized disclosures" to a San Diego Union reporter and for "his lack of candor" during the investigation of the news leaks.

While Hall has not yet been disciplined, the Justice Department said disciplinary action has "been initiated" against him that would reduce his grade (from GS14 to GS13), remove him from his supervisory job and place him on probation. The action has been initiated against Hall for leaking details of the Pendorf investigation to The Wall Street Journal.