On the day his term as director of the Office of Personnel Management expired, Donald J. Devine signed an order that gave him the full authority of OPM director, according to agency documents, even though under law he had to leave that job.

Devine's "delegation of authority" to himself on March 25 was made without the knowledge of acting OPM director Loretta Cornelius, according to OPM and congressional sources. Devine took a job as Cornelius' executive assistant when the requirements of the civil service law forced him to step down as director at the end of his four-year term.

Devine's action could give his critics new ammunition in their battle to block his confirmation to a second term as head of the civil service system.

The General Accounting Office has questioned the legality of Devine's action in a draft legal opinion, according to congressional sources from both parties. They added that the move took some of his Senate Republican supporters by surprise.

The GAO opinion, however, apparently conflicts with an in-house opinion by OPM general counsel Joseph A. Morris, who said in a memo to the Senate Governmental Affairs Committee that Devine's delegation of authority was "properly granted in the interest of sound management."

"There are several different opinions about the propriety, and the question about why this was done behind the scenes," said Charles Osolin, press secretary for the GOP-controlled committee. Osolin added that committee Chairman William V. Roth Jr. (R-Del.) and others were not aware of Devine's action until he resigned from the government May 1 after a publicized dispute with Cornelius.

The committee plans to resume its hearing on Devine's nomination on Wednesday by questioning OPM officials about Devine's action. The GOP controls the committee, 7 to 6, but committee Democrats, who have accused Devine, a conservative Republican, of "politicizing" OPM, are optimistic that they can block his confirmation.

Devine's efforts to cut the federal payroll, curb the pension system and change numerous personnel rules have made him popular among conservative Republicans but extremely unpopular among federal employes and segments of Congress.

Devine and Cornelius are expected to testify at Wednesday's hearing, but neither was available for comment yesterday.

When his term ended and Democratic opposition delayed his reconfirmation, Devine was forced by the Civil Service Reform Act to vacate his job. He then took a $2,800-a-year pay cut, to $72,300, to become Cornelius' executive assistant.

That day, Devine approved a one-sentence amendment to the OPM administrative manual that read: "All investments and delegations of authority to the director are delegated to the executive assistant to the director, who may, in turn, redelegate authority at his discretion."

"Ms. Cornelius knew nothing about it," said a ranking OPM source. "She did not participate in it, nor did she know of its existence" until she began having "conflicts" with Devine about running the agency. After six weeks as her executive assistant, Devine resigned, citing "tangled lines of authority" and saying he would await his reconfirmation.

A former University of Maryland political scientist, Devine is now working temporarily at the Heritage Foundation.

When Cornelius announced that Devine would become her subordinate, she said, "To assist me in my role as acting head of OPM, I have asked Dr. Devine to be my executive assistant. He will report to me and advise me on matters of policy and administration." The announcement made no mention of a transfer of authority from the director's office.

OPM general counsel Morris said in an interview that Devine sought to transfer his authority to his new job because he was concerned that actions he took in his final days as director might be challenged. Morris said that because of delays in publishing OPM actions in the Federal Register, some of Devine's decisions in late March could have been challenged when they were published in April or May because he would no longer have legal authority if the transfer were not made.

Morris said Devine took seven actions as director after his term expired, compared with nearly 100 taken by Cornelius. Morris said Devine's decisions were on "minor" matters, including inviting First Lady Nancy Reagan to an OPM function.