A House subcommittee investigating how Ronald Reagan aides obtained Carter administration documents in the 1980 campaign sent new inquiries to the White House yesterday, and the panel's chairman said there are unconfirmed allegations that sexual favors somehow may have been involved.

The Post Office and Civil Service subcommittee on human resources, chaired by Rep. Donald J. Albosta (D-Mich.), has been given several second-hand reports that intimate relationships between members of the Reagan and Carter campaigns may have been related to the way the documents were obtained.

The panel now plans to question a former campaign insider said to have made the original allegation.

Albosta said in a telephone interview that he had learned of "a possibility of some love affairs between people in the Carter administration and people in the Reagan campaign . . . . We're going to follow these leads."

He said the allegations had been "consistently mentioned" by several "relatively reliable" people from both campaigns. But he cautioned that the accounts were "not first-hand knowledge" and that the matter "should not be blown out of proportion."

He said the possible love affairs could be less important than allegations of "some job promise or some money changing hands."

Albosta yesterday asked presidential counselor Edwin Meese III and deputy chief of staff Michael K. Deaver for the first time what if anything they know about how the Carter documents made their way into the Reagan camp before the 1980 November election.

Meese, told about Albosta's reference to sexual allegations, said, "At no time was there any contemplation or attempt by the Reagan campaign management to get any information out of the Carter campaign."

Albosta also asked White House counsel Fred F. Fielding for a copy of a memo in which Fielding asked hundreds of administration officials to provide any information they have on the incident. In addition, Albosta asked Fielding for the names of those who were sent the memo and for any documents that Fielding obtains from the Hoover Institution at Stanford University, where the Reagan campaign materials are stored.

In other developments yesterday:

* The FBI began interviewing witnesses as part of its criminal investigation into the matter. In separate two-hour interviews, agents from the FBI's Washington Field Office questioned two former aides to President Carter, pollster Patrick Caddell and onetime deputy domestic adviser David M. Rubenstein, who had agreed to cooperate by describing the Carter campaign apparatus and suggesting people to be interviewed.

* Democratic National Committee Chairman Charles T. Manatt called on CIA Director William J. Casey to take a leave of absence until questions about his role in the incident are resolved. "It must be a difficult chore for him to ever brief the president on intelligence matters, if his memory for details is as bad as it appears to be," Manatt said.

* The Albosta subcommittee made preparations to ask former Reagan adviser Richard V. Allen this week to name the person he says provided him with material from Carter's National Security Council staff.

Sources familiar with the FBI investigation said it is at a very preliminary stage. Until yesterday, the sources said, the FBI did not have copies of the Carter briefing documents for the October, 1980, debate with Ronald Reagan, White House press releases on the subject or the responses of senior White House aides to Albosta's inquiries.

For now the FBI is focusing on whether the removal of papers from the Carter White House constituted a theft of government property and who may have done it. A second team of FBI agents has been formed to interview former Reagan campaign aides, including Casey and White House chief of staff James A. Baker III.

The subcommittee decided to interview Allen, a campaign aide who became Reagan's first national security affairs adviser, after Allen said on national television this week that he was prepared to tell appropriate authorities who provided him with staff materials from Carter's National Security Council in 1980. Allen said he received only "innocuous" excerpts from the NSC papers.

Carter's national security affairs adviser, Zbigniew Brzezinski, has said the documents sounded like "extraordinarily sensitive material of the highest order . . . . If that was handed over to anyone outside the White House, it is a very serious crime."

Other former Carter aides said the material appeared to be copies of nightly staff reports to Brzezinski that contained a mixture of classified intelligence items, information on staff assignments and gossip such as internal feuds between NSC officials.