Loretta Cornelius, whose testimony last year doomed her boss' nomination to head the nation's civil service, was fired yesterday as deputy director of the Office of Personnel Management in a terse letter from the White House. But she said she won't leave.

"I cannot be fired by anyone but the president," Cornelius said. "I am going home tonight and coming back into the office tomorrow morning. I'm not turning in my passes or yielding to this kind of thing. I think people ought to be able to speak out, to go before a Senate committee and not get this harassment.

"I have made it clear to everyone that I don't want to stay, and that I don't want another job in the government. I just want all the allegations against me cleared up before I leave," she said in a telephone interview.

Albert Brashear, a White House spokesman, said Cornelius was fired to allow the current director, Constance Horner, to choose her own deputy.

Cornelius contended that her firing is illegal because only the president can dismiss her, but Brashear said she was let go "pursuant to the direction of the president." He declined to comment further on the president's involvement.

If she refuses to be fired, "I doubt we'll do anything on it tonight," Brashear said. "We'll have to talk about it obviously."

Cornelius, 49, jeopardized her future at the government's personnel agency when her damaging testimony before a Senate committee jettisoned the reconfirmation of former OPM director Donald J. Devine, a leading conservative.

Cornelius was the acting director of the agency when she accused Devine before the Senate Governmental Affairs Committee of asking her to lie to the panel.

Devine, who ran OPM during a controversial period of federal retrenchment, was forced to vacate his position as OPM director while awaiting reconfirmation for a second four-year term. Cornelius, as deputy director, briefly succeeded him.

During Devine's reconfirmation hearings, it was reported that he secretly tried to continue running the civil service after his term had expired. Devine became an executive assistant to Cornelius while awaiting confirmation for a new term, having given himself full power to run the agency in the assistant position.

Cornelius testified that Devine failed to tell her of the arrangement, then asked her to lie to a Senate committee and say that she had known about his unusual delegation of authority.

Devine said later that "I should have perhaps done things differently . . . but it was clearly not my intention to hide anything . . . . I can absolutely and without any reservation tell you that I did not tell her or anyone else to lie."

In the face of certain defeat in the Senate, Devine withdrew his name and the White House nominated Horner, who was easily confirmed. But the fate of Cornelius, who reverted to her job as deputy director, remained uncertain as angry conservatives blamed her for Devine's fall.

Soon after, Cornelius said, an anonymous letter was sent to the Office of Government Ethics accusing her of improper use of a government car to travel to and from her home, farm and university classes. The letter also charged that she had OPM staff members improperly type her doctoral dissertation.

"There is nothing there," said Cornelius. "No evidence. I want to be completely exonerated."

OPM asked her to repay $3,565.17 for misuse of the car. She sent the agency a check for $29.07 for the typing, and demanded that all the allegations be cleared from her record.

Her lawyers charged that the guidance on the use of agency vehicles is unclear and has changed several times, and said she was being singled out for harassment.

"It would only take a few seconds to clear up this whole thing," Cornelius said. "These anonymous charges cannot be substantiated, and let's get on with it."

In the meantime, Cornelius said, she has continued to "make speeches, take trips out of town where I had commitments, and talk to associations that have specifically invited me." But Cornelius said Horner asked her staff to exclude the deputy director from meetings.

An OPM spokeswoman referred all calls about her dismissal to the White House.

On Monday, Cornelius said, "I got a call from Alfred Kingon, who worked for (chief of staff) Don Regan . . . . He said that if I would resign by tomorrow Tuesday he would give me a glowing letter from the president and a pat on the back and I could go out with my head held high."

"He said if I didn't resign I would get a different kind of letter," she said. "Last night his secretary called my secretary and asked the status of my resignation. She said she hadn't seen such a piece of paper."

Kingon, White House Cabinet secretary, had no comment on the statement.

"This morning at 11:20," Cornelius said, "the director's secretary walked down the hall and handed me the letter."

It said:

"Pursuant to the direction of the president, this is to notify you that your appointment as deputy director of the Office of Personnel Management is terminated today.

"In closing, I would like to extend my best wishes in your future endeavors. Sincerely, Robert H. Tuttle, director, office of presidential personnel.