President Carter released a voluminous report on the Billy Carter affair yesterday and, taking his case to the public, declared at a news conference last night that the facts will show that "neither I nor any member of my administration violated any law or committed any impropriety."

In a report that was also submitted yesterday to the special Senate subcommittee that is investigating the matter, the president said that Billy Carter has had no influence on U.S. policy toward Libya and that neither he nor anyone else in the White House sought to influence the Justice Department's investigation of his brother's relationship with Libya.

Carter opened the nationally televised news conference with a lengthy statement excerpted from the report to the Senate and sought to turn the controversy to his advantage by recalling the Watergate scandal of the Nixon administration.

Four years ago when he was running for president, he said, "our country was deeply shaken by an administration that had betrayed its trust." His answer then while campaigning, Carter said, was to promise a restoration of intergrity in government. "Integrity has been and will continue to be a cornerstone of my administration," he said.

The report for the most part reiterated earlier White House versions dealing with the controversy and contained no startling new revelations. But the extraordinary document also contained fresh details on the president's thinking as he sought to deal with his younger brother's highly publicized ties to a radical Arab government.

Included in the material released yesterday were personal memorandums dictated by the president for his files and a poignant letter he wrote to his brother while Billy Carter was recovering from alcoholism at a Navy hospital in Long Beach, Calif.

According to these documents, the president made repeated efforts himself and through intermediaries, such as Billy Carter's wife, Sybil, and former budget director Bert Lance, to persuade his brother not to make a second trip to Libya in 1979.

Such a trip, the president said in the April 3, 1979, letter, "would create severe problems for us because of their [the Libyans'] threats against [Egyptian President Anwar] Sadat and because they are fighting in Uganda foar Idi Amin."

The letter continued: "All of us are very proud of you, and particularly your brother! You've had a rough time lately, I know, but you've really come through it with a lot of courage. Call me whenever I can help. I love you. tJimmy."

The White House's account is backed up by supporting documents and 38 pages of statements from national security adviser Zbigniew Brzezinski and White House counsel Lloyd Cutler.

Cutler described a series of regular communications with Billy Carter's lawyers to keep track of the status of the case.

Cutler also said that on two occasions, he specifically asked Attorney General Benjamin R. Civiletti whether there had been contact between the Justice Department and the White House concerning the investigation. Twice Civiletti said there had been none. The attorney general ; later conceded that he had discussed it with the president.

Coming exactly a week before the Democratic National Convention convenes, last night's new conference was a politically critical event for the beleagured president. At first he appeared to be slightly nervous, but soon he seemed at ease, smiling often and occasionally joking as he answered 22 questions.

The bulk of the questions dealt with the Billy Carter matter, and in response the president:

Said he does not know that what his brother did with the $220,000 he received from Libya. But in his opening statement, the president asserted that none of this money has gone to him or to the Carter family peanut warehouse business in Georgia.

Acknowledged that it had occurred to him that his brother might try to use his ties to Libya for financial gain. But, noting that "I don't have authority to order Billy to do something," the president said, "I don't believe that there's anything further that I could have done that would have been effective" in breaking his brother's ties to Libya. Carter was not asked, nor did he say, whether he ever asked Billy Carter if he was being paid by the Libyians.

Defended his use of his brother in the highly controversial role of an intermediary to Libyan officials as part of the U.S. effort to bring pressure on Iran to free the American hostages. But he said that at he time -- three weeks after the hostages were taken -- the fate of the Americans "became an absolute, total obsession of mine" and that he was willing to resort to extraordinary means to free them.

The president praised his brother for undertaking this mission at his own expense, and in about the only acknowledgment approaching regret that he made during the new conference, added:

"I have enough judgment to know that that may have enhanced Billy's stature in the minds of the Libyans, that's the only down side to it that I can understand, and that may have been bad judgment, but I was the one that made the judgment."

Defended his frequent use of relatives such as his wife and mother in diplomatic missions as an often effective tool in dealing with certain countries. The Billy Carter controversy "doesn't mean all the members of my family have to be locked up in a closet," he said.

Rejected a suggestion that White House handling of the case has been "incompetent." Invoking a word that came into vogue during the Watergate scandal, Carter said the mistakes that occurred were caused by the rush to release information, which he said was preferable to "stonewalling."

Denied there was any impropriety in Civiletti's "brief conversation" with him about the case in June. He said Civiletti merely told him the same thing Justice Department officials were telling Billy Carter's lawyers.

Throughout the news conference, the president relied on his brother's well-known reputation for public antics for sympathy and understanding.

"As you know by now, Billy is a colorful personality," he said. "We are personally close. I love him and he loves me. Billy is extremely independent."

After the new conference, as he was leaving the East Room of the White House, the president was asked by a reporter whether he thought his answers to the questions and the report to the Senate panel would end the controversy.

"I don't know," he replied. "It depends on how you all handle it and how the American people judge it."

The release of the report, the result of an intensive White House investigation of the case, and last night's new conference represented an all-oust effort by Carter and his aides to defuse the Billy Carter controversy before the Democratic convention convenes in New York City on Monday.

The case has dominated the news since the end of the Republican National Convention and added fuel to the efforts of supporters of Sen. edward M. Kennedy (d-Mass.) and other anti-Carter Democrats who hope to deny the president renomination in Madison Square Garden next week.

The controversy was set in motion in July when Billy Carter, under pressure from the Justice Department, reluctantly registered as an agent of the Libyan government and disclosed that he had received $220,000 in payments from Libya.

Since then, questions have centered on whether the president or his aides interfered in the Justice Department investigation that ended when the registration statement was filed, and whether the White House, deliberately or not, enhanced Billy Carter's stature and financial leverage with the Libyans by using him as an intermediary in the Iranian hostage crisis.

The president has expressed eagerness to testify before the special Senate subcommitte investigating the case, but that is not likely to occur until after the convention. White House strategists hope that last night's news conference would serve the same purpose in terms of public reaction to the case by displaying Carter as a president with nothing to hide.

To reinforce that point, White House press secretary Jody Powell announced earlier in the day that the news conference, which included a lengthy opening statement by the president, would last an hour, twice the normal lenghth.

The president also sought to take the offensive in the case by announcing that he has instructed his staff to draft a rule on the relationship between government employes and relatives of the president. Almost certain to be known in the future as "the Billy rule," the dictum would "bar any employe of the executive branch from dealing with any member of the president's family under circumstances that create either the reality or the appearance of improper favor or influence," according to the president.

Carter said that in most similar instances involving presidential relatives "the appearance of favoritism has been much worse than the reality," adding, "My brother Billy's case is one of many such examples."

But the president said he remains "deeply concerned that Billy has received funds from Libya and that he may be under obligation to Libya.

"These facts," he continued, "will govern my relationship with Billy so long as I am president. Billy has had no influence on U.S. policies or actions concerning Libya in the past and he will have no influence in the future."

In Americus, Ga., yesterday, Billy Carter told United Press International that he and his brother are now speaking to each other only through their lawyers. "I would not talk to the White House on the advice of my attorneys," he said.

In addition to his own statement, the president also sent to the Senate subcommittee yesterday similar statements on the case by national security adviser Brzezinski and White House counsel Cutler, and a statement dealing with the involvement of others in the matter that was composed by Cutler's staff.

Cutler's report to the Senate subcommittee shows his growing concern, from June 11 onward, with Billy Carter's case. Cutler was kept informed of Billy Carter's intentions by Billy's lawyers, and the White House counsel kept the president informed.

On June 17, Cutler said he was meeting with the president and Civiletti when the attorney general said "he had some other matters to take up privately with the president . . ." Cutler left the room.

He said he later learned that Civiletti discussed Billy Carter's case made public after being reminded of the conversation by Cutler.

On July 14, after Cutler learned that the Billy Carter-Justice Department agreement was to be made public, he tried to confirm from Civiletti that "there had been no contact between the Justice Department and the White House in either direction concerning the conduct of the investigation." Civiletti, Cutler reported, "confirmed that this was correct." A second confirmation occurred July 22.

Brzezinski's statement recounted how the president, saying he was acting on a suggestion from Rosalynn Carter, sought his brother's help in approaching the Libyans on behalf of the hostages in Iran.

The statements were accompanied by a number of unclassified documents. Classified material bearing on the case was submitted yesterday to the Senate Select Committee on Intelligence, according to Powell.

While it contained nothing surprising, the president's statement provided the most complete detail to date on two of the most controversial aspects of the case -- the White House enlistment of Billy Carter as an intermediary in the Iran hostage crisis, and the president's "brief conversation" on June 17 with Attorney General Benjamin R. Civiletti on the Billy Carter investigation.

The president reaffirmed earlier White House statements that the idea to ask Billy Carter to seek Libyan help in the effort to free the American hostages in Iran originated with his wife, Rosalynn.

"As Rosalynn recalls, it occurred to her that Billy might be able to get Libyan help to induce the Iranians to release the American hostages," the president said. "She recalls that she called him and that he agreed the Libyans might help. She informed me of this conversation and on Nov. 20 I asked Dr. Brzezinski to explore this idea further with Billy."

Brzezinski's call to Billy Carter Nov. 20 resulted in a meeting at the White House Nov. 27 involving Brzezinski, Billy Carter, Henry (Randy) Coleman, a business associate of Billy Carter in the Libyan ventures, and Ali Houderi, the chief Libyan diplomat in the United States.

The earlier disclosure of Billy Carter's role in arranging this meeting provoked criticism of the president for using his colorful and often controversial brother in connection with a diplomatic mission. In yesterday's statement, the president went to some length to defend his decision, acknowledging that he had recognized at the time that "there was a risk of criticism in asking Billy to help out."

"The Moslem community places great importance on family ties, and I believed that a request arranged with Billy's participation would be regarded as coming more directly from the president and might supplement the efforts already being made through normal State Department channels," Carter said in the statement.

"Whether it would have been successful if Billy had not participated is a question no one can answer with certainty," he continued. "I made this decision in good faith, with the best interest of the hostages and this nation in mind. Billy merely responed to our request for assistance and I believe his only motive in this effort was to seek release of the hostages."

White House officials have maintained that the Nov. 27 meeting was successful because shortly thereafter Libyan leader Muammar Qaddafi sent a personal message to Iranian officials urging release of the hostages.

The president made clear in his statement that he was aware in 1979 of his brother's mounting financial problems. But he did not deal directly with the question of whether Billy Carter's role in arranging the Nov. 27 meeting may have increased his stature in the eyes of the Libyans. Billy Carter received his first payment of $20,000 from the Libyans less than two months after the White House meeting.

The president's brother has characterized this and a subsequent payment of $200,000 as down payments on a $500,000 loan to him by Libya. The Justice Department has refused to accept the characterization of the payments as loans.

This and other personal memos included in the report provide a rare glimpse into the president's thinking about his brother.

On Feb. 23, 1979, the president dictated:

"I talked to Billy, who's in the hospital . . . We're also trying to work out some resolution of his financial problems. I told Kirbo [Atlanta lawyer Charles H. Kirbo, trustee of the president's financial holdings] to protect Billy's interests in any negotiations concerning the warehouse or Billy's land. And I encouraged Sybil and Randy [Coleman] to discourage Billy from making any other trip to Libya; to try to keep him out of the newspapers for a few weeks; but let him regain his equilibrium."

The next day, the president dictated:

"I talked to Bert Lance this morning. He's to visit Billy this coming week, to encourage him to take care of his health, his finances, and to stay away from Libya for a while."

The president has acknowledged urging his brother to agree to register as an agent of Libya in telephone conversations last June 28 and July 1. He dictated notes on each talk, saying of the June 28 conversation:

"I talked to Billy about his helping Libya and his refusal to sign the foreign agents permit . . . This can become an embarrassing incident later on, particularly with American Jews."

The July 1 note said:

"I called Billy on the phone and urged him to sign the foreign agent certification concerning Libya. I don't know if he'll do it or not. He has been acting as their agent apparently. But he considers himself to be singled out, especially by [syndicated columnist] Jack Anderson and [New York Times columnist and former Nixon White House aide William] Safire -- which is probably true."

On July 7, just a week before Billy Carter filed the registration statement that set off the controversy, the president dictated this note on his brother's status:

"Billy seems to be feeling very good. Not drinking. Tanned. Plays golf. Harrassed by the government on the Libya deal."