Jervis S. Finney, the outgoing U.S. attorney for Maryland, complained yesterday that the failure of U.S. Sen. Paul S. Sarbanes (D-Md.) to recommend to President Carter someone to replace Finney is hurting the operation of the federal prosecutor's office.

Finney, a Republican who has announced he will resign Jan. 31, said that "really great assistants are leaving, others are planning to leave, and still others are discouraged by what they see as a lack of committment up the line."

His successor "ought to be visiting here now, hiring new assistants assuring existing people that important work still will be done, and drumming up enthusiasm," Finney said. "It's really frustrating."

"With the session over, he's working hard on it," the Sarbanes aide said.

A spokesman for Sarbanes said it is "likely" that the senator will recommend a replacement to President Carter by Jan. 1. Although federal prosecutors are nominated by the White House and confirmed by the Senate, the recommendation of a senator in the majority party is generally considered tantamount to selection.

A spokesman at the Justice Department confirmed that as of now "we don't have any strong contenders" for the $46,600-a-year post.

Since President Carter took office, new U.S. attorneys have been nominated in 60 of the 94 federal districts.

The Justice spokesman pointed out that it is not necessary for a new prosecutor to be confirmed before Finney leaves. If there is a vacancy, the chief federal judge for the district, in this instance, Edward S. Northrop of Baltimore, can name an acting prosecutor with full power to operate the office.

Finney served as an interim U.S. attorney during the time between his nomination and confirmation. Finney noted yesterday that though his recommendation was sent to President Ford on Jan. 17, 1975, it was 2 1/2 months, before he was officially nominated, and another six weeks before it was confirmed.

At that pace, Finney said, his successor, if recommended by Sarbanes at the end of this month, would not be nominated until mid-March and confirmed until early May.

The new U.S. attorney will take over a staff of 25 assistants who, since 1970, have conducted investigations of political corruption that led to the conviction on a charge of income tax evasion and the subsequent resignation of then-Vice President Spiro T. Agnew, as well as the convictions of Gov. Marvin Mandel, two county executives and several other lesser public officials.

Barnet D. Skolnik, Finney's chief assistant prosecutor who led the team that conducted those investigations, has indicated he will remain in the office. But Skolnik has been given a special assignment by the Justice Department that will keep him out of the Baltimore office for sometime to come.

Skolnik's chief assistant, Ronald S. Liebman, announced earlier this month he was resigning to join a Washington law firm. Last month, assistants Jerry Martin and Joseph Fairbanks quit to join Baltimore law firms, and Finney said another assistant has told him he plans to leave soon.

"I'm not saying Sarbanes has caused all this leaving," Finney added, "but morale is low."

Finney said the Justice Department has told him not to hire any new assistants so that the new U.S. attorney can fill the vacancies.

Finney admitted that he had sought to remain in the office but was told early in the year by Sarbanes that a change would be made. He said Sarbanes asked him to remain on the job until after the Mandel trial. Finney will become a partner in the Baltimore law firm of Ober, Grimes and Shriver upon his departure from the federal courthouse next month.

Among lawyers rumored as under consideration or seeking consideration for the job are State Sen. Victor Crawford (D-Montgomery), former Montgomery State Sen. James McAuliffe and Baltimore lawyers Alan I. Baron and A. Dwight Petit.