Loretta Cornelius, fired Wednesday as deputy director of the Office of Personnel Management, continued to insist yesterday that the dismissal is not official, and that only the president himself can remove her from office. But she did not follow through on her pledge to go to work as usual.

Joseph J. Petrillo, Cornelius' attorney, said the White House office of Counsel to the President had produced no evidence that President Reagan had mandated Cornelius' firing.

"It's still unresolved," Petrillo said. "She did not go to work today and we are not certain when she will return to her office, if at all. Our position is that the president has the authority to remove Cornelius for any reason, and we are trying to verify that's what has been done."

The letter informing Cornelius of her firing came from Robert H. Tuttle, director of presidential personnel, saying the action was taken "pursuant to the direction of the president."

Rep. Barney Frank (D-Mass.), chairman of the subcommittee on employment and housing of the House Committee on Government Operations, said yesterday he will hold hearings beginning March 5 on "allegations of harassment and efforts by Reagan administration officials to fire Cornelius."

Frank had pledged in December to investigate any harassment of Cornelius that might grow from her testimony during Senate confirmation hearings last year that derailed the nomination of Donald J. Devine for another term as head of OPM.

"The possibility that a high-ranking government official was penalized for telling the truth to a congressional committee is disturbing," said Frank, whose committee has oversight responsibility for OPM.

This round of bureaucratic infighting is the latest to grow from the damaging testimony that Cornelius gave against Devine before a Senate committee last year. She said Devine, a well-known conservative who attracted much criticism for leading the president's drive to revise federal personnel policy, had asked her to lie to the Senate Governmental Affairs Committee. Devine denied the charge.

In an earlier round of infighting following her testimony, an anonymous letter to the Office of Government Ethics accused Cornelius of using a government car to travel to her farm and university classes. She was also alleged to have had government employes type her PhD dissertation.

Earlier this week, Cornelius said she did not want to retain her job or take any other job in the government, but said she wants charges against her "cleared up before I leave."

Cornelius earlier refused requests to resign, and had pledged to go to work yesterday despite her firing. But she did not appear at her fifth-floor OPM office.