A member of West Germany's ruling Social Democratic Party has surfaced a potentially embarrassing issues by asking why his government has failed to take custody of millions of Nazi Party documents that have been in U.S. hands since World War II.

Sources here say millions of the documents -- constituting much of the archives of Adolf Hitler's party -- remain in buildings and underground vaults in West Berlin despite U.S. efforts to turn them over to the West German government.

Parliamentarian Karl-Heinz Hansen, a left-wing Social Democrat, charges that Bonn has resisted taking custody of the archives because they could prove embarrassing to prominent persons here.

The files reportedly contain membership lists, photographs, work applications and numerous other documents. Although West Germany has prosecuted thousands of former Nazis for war crimes, the wartime party membership numbered many millions.

Tuesday, the Justice Ministry issued a harsh rebuttal of Hansen's allegations, saying the documents had all been evaluated and full use of them made many years ago. Thousands of other documents from other countries were also combed for evidence, the spokesman said.

Nevertheless, the archives, known as the Documentation Center, remain in U.S. custody. It is understood that most of the contents have been microfilmed and that the U.S. authorities have wanted to return the facility for years.

The records have been there for 33 years now, having been trucked immediately after the war from the rubble of the battered buildings of the Third Reich -- most of which were in what is now Communist East Berlin -- and stored in what eventually became the U.S.-occupied sector of the divided city.

While the Documentation Center, is no secret, it is not well known publicly either.

It is acknowledged here that West Germans have not yet come to grips with the full legal implications of the material and the issue of how widely available it should be.

A major aspect apparently is whether new right-to-privacy laws that took effect this year might continue to prevent public access to the center. Until now, only a few selected scholars, authors and researchers have been permitted inside.

A spokesman for the U.S. embassy says that information from the center has also been made available for war crime trials in West Germany and that biographical information "from the millions of documents on file" has been provided to various agencies, including prosecuting authorities, in West Germany, the United States, France, and Britain.

"The question of the ultimate disposition of these archives has been discussed between the two governments," the spokesman said, "but a decision on the transfer has been complicated by the needs of both governments to insure that the provisions of their laws regarding public access to government records are satisfied and that adequate safeguards exist to protect the rights of privacy of individuals under the laws of both countries."