Former secretary of agriculture Earl L. Butz will be charged with a criminal violation of federal tax law in a proceeding in Indiana Friday, U.S. Attorney David T. Ready confirmed by telephone yesterday.

Ready corroborated an Indianapolis Star article reporting that Butz would plead guilty to a government complaint charging he had committed the violations after he resigned as secretary.

The Star reported Butz would appear before U.S. District Court Judge Jessie E. Eschbach in Fort Wayne, waive his right to be indicted by a federal grand jury and plead guilty to a criminal information filed by the U.S. attorney's office.

Butz, 71, resigned from the Cabinet of President Ford in 1976 after a racial slur was attributed to him. Since then he has been a professor emeritus at Purdue University in Lafayette, Ind., an active speaker, lecturer and host of his syndicated radio program.

Ready would not comment yesterday on details of the case. He said the criminal information filed Friday would spell out aspects of the case, such as the amount of money involved in the tax violations and source of the funds in questions.

The Star said it was "believed Butz failed to report, and pay taxes on, thousands of dollars earned for speeches and lectures."

Butz would be the fourth member of former president Nixon's cabinet to be charged with a felony. The others were former vice president Spiro T. Agnew, former attorney generals John N. Mitchell and Richard G. Kleindienst and former secretary of commerce Maurice H. Stans. Stans pleaded innocent to nine counts of perjury and attempting to obstruct justice. He was acquitted in 1974.

Butz more recently served on President Reagan's transition team on agricultural policy and has remained active behind the scenes in Republican agricultural politics since leaving office.

His office in Lafayette said yesterday that he was on a speaking engagement in Fargo, N.D., and could not be reached for comment.

The Star said Butz had confirmed earlier that he had cooperated with the Internal Revenue Service in an audit of his tax returns. Ready confirmed yesterday that the Friday hearing could be brief, perhaps no more than 15 minutes.