Rep. Donald J. Albosta (D-Mich.) said yesterday that he has concluded that there was "an organized effort to obtain material" from the Carter White House in 1980 and that "more than one" aide to Jimmy Carter was involved in providing documents to the Reagan presidential campaign.

Albosta, whose House Post Office and Civil Service subcommittee has been investigating the acquisition of Carter papers by the Reagan campaign during the 1980 election, declined to give specifics, saying he wanted to preserve the probe's secrecy. He said he would detail some of the findings next month at the first of two planned public hearings.

Albosta spoke to reporters after successfully urging the House to pass a five-year reauthorization of the Office of Government Ethics, which is scheduled to go out of business Sept. 30. Albosta said he may propose further amendments to the ethics act to deal with the kind of allegations he is investigating.

"The trend seems to indicate that there was some organized effort to obtain material . . . from the Carter White House for informational purposes for the Reagan-Bush campaign," Albosta said. He said the subcommittee still is focusing on indications that some material may have been taken from Carter's National Security Council.

Albosta said his staff has interviewed about 75 people and that he now expects to "get to the bottom" of the mystery. By the time the probe is finished, he said, "I believe we will be able to indicate someone did it."

Albosta also said he has reached agreement with the White House to allow congressional investigators to inspect new Reagan campaign files stored at the Hoover Institution at Stanford University.

He said these would include the personal campaign files of White House counselor Edwin Meese III and of Robert Garrick, a retired admiral who helped the Reagan campaign monitor military bases in case of an "October surprise" by the Carter White House.

Albosta said some personal files--including those of White House chief of staff James A. Baker III and CIA Director William J. Casey--were not located in California, but that his staff has been able to inspect them in Washington. He added, however, that the FBI has been "slow" to provide the panel with information from its criminal investigation.

The measure extending the five-year-old Office of Government Ethics plugs several "loopholes" in the law, Albosta said. The bill would allow the office to draft government-wide ethics regulations, to review financial disclosure statements of 69 additional White House aides and to extend disclosure requirements to some members of advisory committees. The bill also would require persons nominated by the president to high-level jobs to update their financial disclosure statements before their Senate confirmation hearings.

Aides said this was in response to a 1981 incident involving Attorney General William French Smith, who did not report a $50,000 corporate severance payment that he received shortly after filing his disclosure statement.

The House measure must be reconciled with a Senate version that would give the ethics office director a fixed tenure that would not coincide with the president's term.