Two of the three chief editors at the West German newsweekly Stern resigned today in the aftermath of government findings yesterday that the purported diaries of Adolf Hitler were blatant forgeries.

The magazine issued a statement from its Hamburg headquarters saying Peter Koch and Felix Schmidt had offered their resignations. Stern publisher Henri Nannen and the third chief editor, Rolf Gillhausen, will now assume full editorial responsibilities.

Two weeks ago, Koch and Schmidt appeared at a press conference with Stern reporter Gerd Heidemann, who claimed to have uncovered the diaries, to respond to suggestions that the 62 volumes, bound in imitation black leather, were not authentic.

Heidemann could not be reached for comment after West German archivists and crime experts announced that, on the basis of studying seven volumes, they had found them obvious fakes since the paper and glue had been concocted years after the dictator's death.

Heidemann contends that he tracked down the diaries after a three-year hunt through Europe and South America, but he has refused to reveal the source of his discovery because he claims it would endanger persons involved.

Stern publisher Nannen, who canceled further publication of excerpts yesterday, said, "We will fully clear up the matter for we have no reason to protect the swindler."

Leading West German newspapers today urged Stern to clarify the murky origins of the fake diaries. "Its greed for a million-dollar scoop far exceeded its competence," proclaimed the conservative daily Die Welt in an editorial, adding that it was important to unveil the identity of the forger and the motives behind "this historic lie."

A Stern reporter for more than three decades, Heidemann, 51, is known to have cultivated acquaintances among ex-Nazis living in Europe. Nearly 10 years ago, he purchased the yacht of Hermann Goering, the former Nazi air force chief. He has admitted that the trail toward the purported diaries was instigated by his contacts with ex-Nazis, who were drawn to him by his interest in collecting Nazi memorabilia.

Heidemann said he finally embarked on an odyssey that took him to East Germany, where he uncovered remnants of a crashed plane that historians suspect was carrying Hitler's personal papers in April 1945.

But Heidemann has declined to provide accounts, even confidentially to his editors, of how he traced the diaries from the crash site in East Germany.

Hans Booms, president of West Germany's federal archives, said yesterday that the primitive nature of the diary forgeries and the "source material"--a book of Hitler's speeches compiled in the early 1960s--pointed toward right-wing elements or unreformed Nazis.

Notable scholars like Joachim Fest, a noted biographer of Hitler, and Eberhard Jaeckel, another expert on the Third Reich, say they were approached about three years ago by a Stuttgart industrialist peddling papers and paintings signed by Hitler. Both men said they spurned the material because of doubts about authenticity.

After learning of the fake diaries' contents, Fest said that he was convinced they were the same as the documents he perused three years ago. "The trail to those diaries," he said in a recent telephone interview, "only led as far as Stuttgart."

In London, The Sunday Times said, "We owe our readers a sincere apology" for having started to publish the alleged diaries, now canceled.