Errol Flynn, the movie star best remembered as Robin Hood and Captain Blood, was a swashbuckler for Der Fuhrer, a new biography claims.

According to Charles Higham's "Errol Flynn: The Untold Story," which Doubleday will publish in April, the Australian-born actor spent over five years working as a Nazi agent.

Higham claims the book is based on over 5,000 U.S. government documents obtained through Freedom of Information Act requests to the State Department, Army and Navy intelligence, CIA, OSS and FBI.

One FBI official contacted for possible verification last night said he knew nothing of the case, but asked plaintively, "Next you're going to tell me that John Wayne was a KGB agent?"

However, other officials at both the FBI and the State Department acknowledged that Higham had received copies of government files on the late actor. And one State Department source confirmed that some State documents did raise the "possibility" that Flynn was working for the Nazi cause.

A Doubleday source said last night that, according to the book, Flynn began spying on German supporters of the Loyalists during the Spanish Civil War and reported on them to the Nazis. The Doubleday source claimed that these charges are supported by State Department files.

"At one point in his career," Higham said in a telephone interview, "Flynn intervened with his friend Eleanor Roosevelt to prevent a German agent from being deported before the attack on Pearl Harbor."

The book alleges that in 1940 Flynn was instrumental in getting Warner Bros. to shoot portions of the film "Dive Bomber" on location at Pearl Harbor and the San Diego Naval Base, and later arranged for the Japanese government to get an advance copy of the film.

"This gave them a tremendous advantage," Higham said last night, "particularly in revealing the catapult systems on U.S. aircraft carriers. I believe Flynn took special pleasure in knowing that a studio owned by a Jew (Jack Warner) was helping the German war effort. Flynn was terribly anti-Semitic. When Warner would come on one of his sets, Flynn would scream, 'Get that Jew out of here!"

The allegations about Flynn, who starred in several anti-Fascist films during the war, are the newest entries in the vogue of tarnishing the tinsel of Hollywood. In the past five years, various books have claimed that Montgomery Clift was a deranged homosexual, Joan Crawford a sadist and Marlon Brando a lousy lover. About one-third of the Flynn biography delves into his alleged work for the Nazis; other parts chronicle his drinking bouts and bisexual life-style.

Higham said last night that he became fascinated with Flynn several years ago when the late Robert Lord talked about Flynn's behavior on "Dive Bomber," which Lord directed.

"Lord made me swear that, I would never do this while he was alive," said Higham, who has written many books on Hollywood figures, including Katharine Hepburn, Marlene Dietrich and Orson Welles.

"Flynn was generally very bored while he was working," Higham said. "But he was particularly animated on 'Dixie Bomber,' even spending two months living at Pearl Harbor before shooting began. Lord was very troubled by Flynn's friendship with Hermann Urban, [an alleged Nazi agent]. He told me that he had brought this matter up several times in Washington, but that he was always blocked.

"So I started making inquiries to the government, and became amazed at what I found. I spent about 18 months researching this in five trips to Washington."

Last night, from his home in Los Angeles, Higham quoted from several government documents. A May 1944, FBI report, he said, called Urban "an agent of the German government," said Flynn was his "only American contact" and alleged that Flynn smuggled Urban into Mexico aboard his yacht. c

A State Department memo dated Jan. 18, 1943, records "telephone intercept SATP 9891 from Errol Flynn to [blanks]. F.C. understands that Flynn was recently in Mexico at which time he associated with [blank], German national and enemy agent."

A Warner Bros. internal memo to its legal department reports a visit from an immigration officer who wanted to issue a deportation warrant for Flynn (a British subject) on the grounds of "possible espionage."

An FBI official last night stressed the importance of understanding that many government documents are merely "raw files."

"As has been too painfully revealed in the past," he said, "a lot of things written in those memos, particularly in times' of national crisis, err on the side of the government."

Higham claimed last night that his book pieces together a giant jig-saw puzzle scattered throughout the files of the federal bureaucracy.

"I think that the government allowed Flynn to stay in this country because he was leading them to a number of enemy agents. At one point, when the government was attempting to deport Urban, Flynn flew to Miami to intercede with Elanor Roosevelt.He had known her through her son Franklin Jr. and their mutual friends the Whitneys. The Roosevelts knew that Flynn was an anti-semite, and used to drive him up a wall by calling him Flynnberg.

"When he arrived in Florida, Mrs. Roosevelt was so taken with his story [that Urban was being maligned] that she had Urban hired to work as a doctor in a CC camp."

Higham said -- and government sources confirmed -- that Urban was ultimately deported. "He turned state's evidence at the Shanghai war trials, and then was taken to Germany and tried at the Spandau trials. Although never convicted, he spent 2 1/2 years in German jails.

"I finally tracked Urban down," said Higham. "I went through 13 AMA volumes listing doctors abroad, and found an address for him in Sumatra. I finally contacted an associate of his, who tole me he's working up in a mountain leper colony."

And then, ever the self-promoter, Higham paused.

"I haven't even told you the best parts of the book," he said.

'You'll have to wait for those."