Insisting that he had not been tipped off, Billy Carter said yesterday that he had no idea that the Justice Department already knew of the $220,000 he got from the Libyan government before he admitted taking the money.

The presient's brother said that as far as he was concerned he was the first one to tell government investigators about the payments. In a June 11 interview at the Justice Department, which he had initiated, he acknowledged receiving the money.

"I've seen several reports that they found out earlier, and then I found out they knew about it, but that's not true," Carter said in an interview on ABC-TV's "Good Morning America" program.

Justice Department officials have said that they first heard about the payments in late May and confirmed the reports on June 2. Some government officials reportedly have voiced suspicions that Billy Carter had been warned about the Justice Department's discovery when he arranged the interview on June 10, the day before it took place.

"I have cooperated, regardless of what the Justice Department says," Carter maintained yesterday morning in a separate interview after his televised appearance. But he was vague on what prompted him to seek the June 11 meeting at Justice with Joel Lisker, the head of the Department's foreign agents' registration unit.

Carter said only that he wants to see Lisker personally because Lisker would not take telephone calls from the Georgia lawyer Carter had asked to check on the status of his case. "I wanted to get finalized," he said.

In a foreign agent's registration statement he was forced to file last week, Carter described the payments -- $20,000 in Janaury and $200,000 in April -- as installments on a promised $500,000 loan from the Libyans, although no loan agreement has been executed.

Carter had given no indication of the arrangement when government investigators interviewed him in January at his home in Buena Vista, Ga.

Despite earlier denials, Billy Carter also said yesterday that he spoke with the president about his Libyan dealings "a couple to three weeks ago." That would place the conversation in early July, before anyone at the White House had indicated an awareness of any of the details of Billy Carter's Libyan dealings.

"He [the president] talked to me one time," Billy Carter said. "He called me and said, 'Can I give you some advice?' . . . And I said, 'Hell, Jimmy, everybody else is, you might as well, too.'

"And he said, 'Why don't you make a full disclosure?" which I did. It's public record. I made a full disclosure of everything I've ever done for the Libyans. And they have never asked me to do anything."

President Carter alluded to the conversation last Thursday in Jacksonville, and said it had occurred "just a few days ago." The White House last night said it took place July 1.

Following his June 11 meeting at the Justice Department, which took about an hour, Billy Carter said he went to the White House for a meeting with national security adviser Zbigniew Brzezinski, an appointment he had also arranged on June 10.

Carter said he went to see Brzezinski "about something that is not connected with my case," and, in the course of that discussion, "I told him a little bit about what was going on with the Justice Department."

He said Brzezinski referred him to White House counsel Lloyd Cutler concerning the Justice Department inquiry. He said Cutler told him "I probably needed a Washington lawyer" and mentioned "four or five law firms" to consider.

The president's brother said he piced out attorneys Stephen J. Pollak and Henry S. Ruth Jr., partly because they had represented White House chief of staff Hamilton Jordan previously. "I felt they would understand my accent after working with Ham," Carter said.

In the registration statement he filed July 14, Billy Carter also said he had been dickering with Libyan officials since the spring of 1979 about an increased allocation of Libyan oil for the Charter Oil Co. of Jacksonville.

No agreement has been reached, but Carter evidently stood to earn millions of dollars a year in commissions for his efforts. Carter proposed to get 100,000 barrels a day for the company through his ties to the Libyans, and a Charter executive, in a tentative agreement last August, said the company would pay him as much as 55 cents a barrel for his efforts.

The letter of agreement was signed by Lewis I. Nasife, president of the Charter Crude Oil Co., a subsidiary responsible for the company's oil supplies. It was dated Aug. 21, 1979, four days after Nasife met with Billy Carter at his Buena Vista home to discuss the proposition.

In the letter, Nasife said that during "times of short crude supply, we, Charter Oil Co., would agree to pay 55 cents per barrel on all barrels listed [delivered] as a result of your efforts." He added that the fee would be lowered to a minimum of 5 cents a barrel if market conditions changed.

That would have given Carter at least $1,825,000 in a single year at 5 cents a barrel and as much as $20,075,000 at 55 cents a barrel. Charter executives said that Carter would have been paid the premium rate until about mid-January of 1980 when market prices for refined products fell. At that point, the executives said, the commission would have been lowered to 5 cents a barrel.

Charter Oil had been getting 100,000 to 125,000 barrels of Libyan crude oil per day for its huge Bahamian refinery when Carter approached it. It was cut back on May 1 to 60,000 barrels a day.

In a related development. Justice Department officials disputed a published report that they had failed to pursue leads that tied Billy Carter to an alleged bribery plot.

The New York Times reported yesterday that a federal grand jury in New York did not follow up on the charges that Carter was involved in a plot to get administration officials to allow Libya access to some U.S.-made military planes it had purchased but had not been permitted to receive.

One official familiar with the case said the allegations came from a source who claimed he could deliver evidence showing Carter's connections to the scheme. But the evidence was never produced.

"We've followed all the leads in this case to the nth degree," he said. "As far as Billy Carter is concerned, there is no evidence."

Other sources said the man who made the claim was facing imminent indictment on fraud charges and since has been indicted in three western states.