The Senate Judiciary Committee expects to question Francis L. (Bud) Mullen Jr., acting head of the Drug Enforcement Administration, within the next month about allegations that he gave misleading testimony at 1981 confirmation hearings for Secretary of Labor Raymond J. Donovan.

A spokesman for the Judiciary Committee said it also is studying a legal memorandum asserting that Mullen has been acting without proper authority at the DEA for almost two years because of an old and rarely cited federal law governing temporary appointments.

Mullen's nomination as DEA adminstrator has been bottled up since last June while the Senate Labor Committee has investigated what it called "remaining, unanswered questions" about his role in the FBI's pre-confirmation investigation of alleged ties between Donovan and organized crime.

The Labor Committee yesterday formally issued a special staff report accusing Mullen, who is still an FBI executive assistant director and who was in overall charge of the Donovan inquiry, of misleading the senators and deliberately holding back pertinent information about the case.

A special prosecutor later concluded there was "insufficient credible evidence" to warrant Donovan's prosecution on any charge, but the special Senate report said the committee should have been told much more about the allegations so it could have weighed them properly.

The study charged that the FBI failed to follow its own investigative guidelines for the Donovan inquiry, and recommended that Congress enact legislation to make sure it gets all the information the FBI develops in such cases.

Mullen came under fire for what he described in a Washington Post interview last June as a conscious decision not to tell the Labor Committee that Donovan's name had been mentioned on an organized crime wiretap in New York City.

The committee report noted that the FBI official in immediate charge of the Donovan inquiry, Anthony Adamski, had characterized the taped reference as "pertinent," but Mullen disputed that and defended his actions on the grounds that the conversation in question "didn't indicate any criminality on the part of Ray Donovan."

Mullen told the Labor Committee on Jan. 27, 1981, in his prepared testimony, that a check of "electronic surveillances" by "the FBI in New Jersey" revealed no mention of either Donovan or the Schiavone Construction Co. of Secaucus, where Donovan was executive vice president.

In short, yesterday's report charged, Mullen "decided to mention the wiretap search in New Jersey that disclosed nothing and to withhold the earlier search in New York that uncovered Masselli's tape reference to Mr. Donovan." The reference was to alleged Mafia figure William Masselli.

Questioned about the sequence in an executive session last August by Senate Labor Committee Chairman Orrin G. Hatch (R-Utah), Mullen took exception to the suggestion that he mentioned the New Jersey "overhears" at the outset of his 1981 testimony in order to avoid discussing the Masselli tapes themselves.

He said, "That was not my primary purpose . . . . That information about the New Jersey wiretaps was to further assist the committee . . . something else to help them make up their minds."

By contrast, in his tape-recorded interview with several reporters last June, Mullen was asked this question and gave this answer:

Q.: " . . . I know you testified in your prepared statement about New Jersey, and you did that very artfully and consciously because you didn't want to spill the Masselli beans, right?"

Mullen: "Yep."

A spokesman at the DEA said yesterday that Mullen had no immediate comment.