Former Reagan aide Wayne Valis has told federal investigators the names of two people outside the Carter White House and campaign--one of them now a Reagan National Security Council staff member--who he said were the sources of a memo he received in 1980 supposedly describing a Carter staff "brainstorming" session about the upcoming presidential debate.

The FBI has interviewed both the men Valis named--John Lenczowski, a Soviet and east European affairs expert on the National Security Council staff, and Robert D. Leahy, a Washington public relations executive--as part of the Justice Department investigation of how Carter debate preparation materials and other documents wound up in the files of assorted Reagan 1980 campaign aides.

Valis has maintained to federal investigators that he does not know the source in the Carter staff who initially provided the information that he forwarded to top Reagan campaign officials. He also has suggested that the memo was not written inside the Carter camp but was done by outsiders who simply were reconstructing things they had been told.

Lenczowski declined to comment on specifics of the case yesterday except to say: "I've cooperated with the FBI. I have told them everything to the best of my recollection . . . . I have a clear conscience."

He said in a telephone interview that he served as an "unofficial consultant" to the Reagan campaign, providing information to campaign officials through "several different informal channels."

He said he mainly provided "policy briefs" to the Reagan campaign through Valis, whom he said he knew at the American Enterprise Institute, a Republican-oriented think tank here. At the time of the 1980 campaign, Lenczowski was employed as an aide to Rep. James A. Courter (R-N.J.) and taught government and politics at the University of Maryland.

Leahy, interviewed separately, denied that he provided the information contained in the memo that Valis forwarded to senior Reagan campaign officials.

"I don't know where that memo came from," he said. " . . . I did not draft, write, come up with anything that was in that memo." He added that he did not meet Valis until after the campaign was over, when he went to a party at the American Enterprise Institute to celebrate publication of a book Valis wrote about Reagan.

Leahy said he did on occasion provide Lenczowski, whom he called a good friend and classmate at Johns Hopkins School of Advanced International Studies, with information and ideas to be passed along to the Reagan campaign. Leahy lobbied and did public relations for several foreign clients, and said that on occasion he was inside the offices of the Carter National Security Council staff members on the business of his clients.

At the time Leahy worked for Ernest Wittenberg Associates; in August, 1981, he joined The Hannaford Co., the public relations firm of longtime Reagan associate Peter Hannaford.

Leahy also said that on occasion he would be told things--"and sometimes I'd even overhear someone talking in a bar or a restaurant, like maybe The Palm"--and that he would pass that information on to Lenczowski as well.

A few of the points contained in the memo forwarded by Valis contained items that Leahy said he might have mentioned to Lenczowski as information that he had been told or overheard. But he emphasized that he never provided a detailed, 10-point listing or anything resembling the memo that has since become public.

Copies of two memos Leahy wrote to Lenczowski were found in Lenczowski's files and were made available to federal investigators, Leahy said. He described both as standard campaign fare, dealing with his own thoughts and not with inside Carter information. One offered "public relations" advice, he said, and the other "a list of potential dirty questions that could come up to Ronald Reagan during the campaign . . . or debate."

According to informed sources, Valis has told federal investigators that he got the one page, 10-point memo entitled "Proposed Carter Tactics for Debate and Campaign Advertising" from Lenczowski, and that he did not know who prepared it.

Sources gave this account of what Valis has told federal investigators:

Valis said Lenczowski told him during the campaign that a friend outside the Carter White House and campaign, whom Valis believes was Leahy, had a conversation with someone who provided this inside information on Carter's tactics.

Lenczowski first passed this on to Valis orally. Valis said he then told Lenczowski he wanted the information in writing, and that sometime after that, Lenczowski provided him with the document outlining the 10 points. At the time, Valis has said, he had not met Lenczowski's friend, Leahy, but that they have since met.

Valis said he wrote a covering memo to the document and forwarded it to senior Reagan campaign officials David R. Gergen, now White House director of communications, and his campaign superior, James A. Baker III, now White House chief of staff. Valis' handwritten covering memo, addressed to Gergen and dated "10-21-80," said:

"These notes are based on a Carter debate staff brainstorming session--middle level types--nothing spectacular, but interesting--from a source intimately connected to a Carter debate staff member. Reliable. I gave a copy to Jim Baker."

Valis maintains now that he used the "intimately connected" reference only as a way of "twitting" Gergen, whom he knew when they were both members of the Nixon and Ford White House staffs, and later when both were at the American Enterprise Institute.

Valis said in a telephone interview that he had cooperated with authorities and would make no other public comment.

"I've told them who I talked with and who my contacts were with," Valis said.

The one-page typewritten memo attached to Valis' handwritten covering sheet contained 10 points that Carter allegedly planned to raise during the debate or that his advisers allegedly intended to do in the last days of the campaign.

Former Carter officials have said they remember no "brainstorming" meeting where such points were discussed, although then-domestic policy adviser David Rubenstein, who prepared Carter's domestic questions and answers, did convene one meeting in the Roosevelt Room during the debate preparation period so that all aides who wanted to make suggestions could do so. About 35 Carter aides attended that meeting, he has said.

Carter aides added that most of the items in the memo appear to have been either common sense or common knowledge in the Carter campaign. But federal investigators have been interested in the memo in part because of the possibility that whoever passed on that information may have passed on other information on other occasions--which could be important to the probe of how pages of Carter debate questions and answers wound up in the hands of the Reagan officials before that pivotal Oct. 28, 1980, debate.

The memo came to national attention when it was included among the papers from the files of Reagan campaign officials that the Reagan White House made public on June 28. Leahy recalls that Valis recently contacted him.

"He called me and asked me to look at it the memo and see if I knew where it came from," said Leahy. Leahy said he told Valis he never saw the memo before. "I don't know why he thinks it's me when I didn't even know him then," said Leahy. "He keeps saying maybe it came from me or John."

He added that Lenczowski was angry at being mentioned by Valis to federal authorities.

Lenczowski, 32, joined the staff of under secretary of state for political affairs Lawrence S. Eagleburger after the inauguration. Before that, he served as an aide to Courter and as a staff member at the American Enterprise Institute.