The trial of House District Committee Chairman Charles C. Diggs Jr. (D-Mich.) on charges that he defrauded the U.S. treasury of $101,000 has been postponed until Sept. 26.

Diggs' attorney, Vincent I. Fuller, asked for the postponement yesterday, saying he had not had "adequate time" to prepare Diggs' defense. Fuller also had said earlier that the previous June 16 trial date would interfere with travel plans he had made.

The postponement means Diggs, a member of Congress for 23 years, will go on trial after the Aug. 8 Democratic primary in Michigan. Diggs has no announced opposition in that race so far.

Diggs is accused in a 35-count indictment of defrauding the U.S. Treasury by manipulating his congressional staff payroll for his own personal gain.

The indictment accuses Diggs of placing three employes of his Detroit funeral home firm on the congressional payroll when they did no government work, and inflating the salaries of three other congressional employes with the understanding that they would use the money to pay some of his personal bills.

The case is assigned by U.S. District Judge Joseph C. Waddy, who has denied pretrial defense motions that the case against Diggs be dismissed.