NEW YORK (AP) – An author who has researched the Cold War’s most famous espionage case said new evidence suggests another American diplomat, not Alger Hiss, was the Soviet agent who fed American secrets to Moscow. Also at the conference, a stepson of Hiss argued that Hiss’ chief accuser invented the spy allegations after his sexual advances were rejected.

Author Kai Bird said there was new evidence to suggest that the real spy was another American official named Wilder Foote. Hiss was accused of feeding secrets to the Soviet military intelligence agency GRU under the code name Ales.

Mr. Bird said he and co-researcher Svetlana A. Chervonnaya had identified nine possible suspects among American State Department officials present at the American-Soviet Yalta conference in 1945. A process of elimination based on their subsequent travels to Moscow and Mexico City excluded eight of them, including Hiss, he said.

“It left only one man standing: Wilder Foote,” Mr. Bird said.

Foote, a member of a well-known Boston family, died in 1974 after a career as a diplomat and owner of a string of newspapers. During World War II he was involved with American lend-lease operations supplying the Soviets.

The key, according to Bird, was that Ales’ contact at the Soviet embassy in Washington would have known that Hiss, a top-tier diplomat who later played a key role in founding the United Nations, had returned from Mexico City, whereas Ales was known to have remained there.

That information was in a secret Soviet cable that was intercepted and decoded by American intelligence agencies and is now part of the so-called Venona Papers, a collection of such documents made public several years ago.

In a telephone interview, Mr. Bird said that more research would be required to prove that Foote was Ales but that “he fits the itinerary in every way, and Hiss simply does not.”

Responding to a query by The Associated Press, Foote’s grandson said in an e-mail signed “Wilder Foote 5” that his grandfather “was cleared of any suspicion” of wrongdoing by the FBI and the McCarthy Commission investigating spy activities. “He was and still is innocent.”

“I can only assume that Mr. Bird has ulterior motives to besmirch my grandfather’s name, possibly for Mr. Bird’s own celebrity,” he added. “Quite convenient for him that everyone involved is dead and cannot speak in their own defense against allegations.”

“Mr. Bird’s unsubstantiated statements will undoubtedly damage my grandfather’s name with little or no recourse on my part … I am glad that my grandfather is not here to endure this sort of attack,” said Mr. Foote, a commercial pilot who lives in Belleville, Mich.

Mr. Bird quoted the elder Mr. Foote as saying earlier, “I am confident that the actions of my father will ultimately be proven to be above reproach.”

Also Thursday, Timothy Hobson, an 80-year-old retired surgeon who was Hiss’ stepson and grew up in the family home in Washington, D.C., said Whittaker Chambers, whose bombshell allegations against Hiss broke the case open, had lied about his personal relationship with Hiss and had never visited the Hiss home as he claimed.

Mr. Hobson said that during the time Chambers claimed to have visited the home, he was recuperating from a broken leg and met every person who came calling.

Chambers was a former American communist party member who spied for the Soviets during the 1930s. He defected before World War II and accused others of being spies, but his claims did not attract FBI interest until after the war. He joined Time magazine in 1939 and as a writer and editor was a severe critic of communism. He died in 1961.

“It is my conviction that he was in love with Alger Hiss, that he was rejected by Alger Hiss and he took that rejection in a vindictive way,” Mr. Hobson said.

Among the speakers arguing that Hiss was guilty, author G. Edward White said Hiss supporters use a “thread strategy,” seizing on any “inconsistency” to unravel a scenario aiming to vindicate him of the spy charges.

Whether Hiss was Ales need not rely on a single piece of evidence, Mr. White said. There is no reason that pieces of evidence must corroborate one another, and “we can’t say that the absence of evidence is evidence,” Mr. White said.