Justice Lewis F. Powell yesterday offered a tart rebuttal to media portrayals of a feuding, leaderless Supreme Court, calling that image "wholly inaccurate" and "nonsense."

Powell, the first justice to defend the court publicly from recent criticisms, carefully avoided mention of the best-selling book, "The Brethren." But his speech, prepared for delivery last night in Dallas, focused on the theme of the book, and it seemed obvious what he was talking about.

"The American people have respected the courts," Powell said, "and they have placed special trust and confidence in the Supreme Court! . . . Those who denigrate it do a disservice to liberty itself."

Powell also issued a broad criticism of those who believe a "Nixon bloc" on the court set out to "dismantle the great decisions of the Warren Court."

". . . . This woeful expectation has not been realized," Powell said, but "now the criticism is that we are leaderless and unpredictable.

"I have wondered whether those who decry the 'rudderless court' would like to be judged by a different kind of court. . . . What confidence could a litigant have in a court that decided cases according to some consistently applied philosophy or 'theme,' rather than on the facts of his case and the applicable law?"

While it is common for justices to give speeches, none of the nine has had anything to say about "The Brethren," written by Bob Woodward and Scott Armstrong of The Washington Post, and published in December. Neither have they commented on the book's critical theme, which already had surfaced in other media and scholarly accounts.

The book, now a source of controversy among lawyers and judges, used thousands of previously secret internal documents and interviews with clerks and justices as the basis for its portrayal. Warren Burger was pictured as a chief justice little-respected by any of his colleagues, including Powell, who once reportedly told a clerk that he would have fired any law practice associate who wrote opinions as badly as did Burger.

Justice William Brennan was said to have called Burger "dummy" in front of his clerks. That was said to reflect a general personal tension among various justices.

The image of a court "torn by personala discord and lack of mutual respect," Powell said, ". . . is a wholly inaccurate picture of the relationships at the court. At the personal level, there is genuine cordiality. No justice will deny this. We lunch together frequently, visit each other's homes, celebrate birthdays, and enjoy kidding each other during our long and demanding conferences.

". . . Misconception as to differences among the justices is not confined to the media," he said. "Law clerks . . . may take personally the professional disagreements among us. A clerk's loyalty to his or her justice tends to be high. This sometimes may cause a clerk -- disappointed by the outcome of a particular case -- to think harshly of justices who have disagreed with his or her 'boss.'

". . . Few of our opinions will ever make a best-seller list. Assuring that news stories about the court will be readably may well require some romancing about our disagreements," Powell said.

"There are recurring demands that the public and the media have frontrow seats on the decision-making process" of the court, he said.

But "The integrity of judicial decision-making would be impaired seriously if we had to reach our judgments in the atmosphere of an ongoing town meeting. There must be candid discussion, a willingness to consider arguments advanced by other Justices and a continuing examination and re-examinations of one's own views.

"Our decisions concern the liberty, property and even the lives of litigants. There can be no posturing among us, and no thought of tomorrow's headlines.