The author of a best-selling book that attacked the credibility of Anita F. Hill has disavowed its premise, and now says that he lied in print to protect the reputation of Justice Clarence Thomas.

David Brock, the author of the book, ''The Real Anita Hill'' (Free Press, 1993), has also suggested, in a magazine article to be published this week, that Justice Thomas used an intermediary to provide Mr. Brock with damaging information about a woman who had come forward to provide support for Ms. Hill's accusations of harassment by Justice Thomas. Ms. Hill's accusations became the focus of Senate hearings into Justice Thomas's nomination to the Supreme Court in 1991.

Mr. Brock reported that he then used the information to force the woman to retract her statements about Justice Thomas. The article, in the August issue of Talk magazine, is excerpted from Mr. Brock's new book, ''Blinded by the Right: The Conscience of an Ex Conservative'' (Crown Publishers), which is scheduled to be published in September.

Describing an article he wrote for The American Spectator, a conservative magazine, in 1992, which became the basis for his book on Ms. Hill, he said he did everything he could to ''ruin Hill's credibility,'' using ''virtually every derogatory and often contradictory allegation I had collected on Hill into the vituperative mix.''