The CIA's former chief historian is challenging the agency's secrecy rule, saying it illegally bars him from releasing a report he wrote on the disastrous 1961 Bay of Pigs invasion of Cuba.

The CIA is trying to avoid embarrassment by barring release of the report, former historian Jack Pfeiffer said in a lawsuit filed in U.S. District Court Tuesday. The agency should not be allowed to keep unclassified information secret, he said.Pfeiffer, a 70-year-old CIA retiree who lives in Alexandria, Va., wants to release a report he wrote in the early 1980s on the CIA's internal investigation into the failed Bay of Pigs invasion.

"The agency should have done a helluva lot better job on the internal investigation," Pfeiffer said in an interview. "This was a critical episode when the Bay of Pigs collapsed around their ears."

It was 30 years ago this month that CIA-backed Cuban exiles tried to invade their homeland by landing at the Bay of Pigs. The fiasco was a major embarrassment for the Kennedy administration and for the CIA.

Pfeiffer, who worked for the agency from 1955 to 1984, said his report contended the CIA inspector general's investigation of the failed invasion was biased and was conducted by unqualified personnel.

Pfeiffer's lawsuit seeks to overturn the CIA's secrecy regulation that bars current and former agency employees from disclosing official information - classified or unclassified - unless disclosure is required as part of their official duties.

He is represented by the Ralph Nader group Public Citizen.