Carter administration appointees in many agencies are tightening their control by adding a new layer of political or confidential aides responsible to them. Some, also are making plans to convert some key career jobs to the political Schedule C.

Several Cabinet officers have asked their legal offices to check regulations to see if they can convert administrative officer jobs - now held by careerists - to political appointments. They also are planning to extend political appointents to field positions now held, at least nominally, by career civil servants.

The two most powerful federal agencies in terms of controlling the bureaucracy's personnel policies (Civil Service Commission) and money (Office of Management and Budget) also are adding new layers of political authority.

CSC, the government's merit watch-dog agency, yesterday created seven new Schedule C. slots. They are to support the three new commissioners (two Democrats and a Republican). The Schedule C aides will be the first political appointees added to the CSC since it was created.

OMB, which got an influx of political appointees during the Nixon years, now has even more under Carter. Two high-levl political jobs called executive associated directors have been added. They form a layer above associated directors, who also are noncareer appointees.

In addition, CMB has six new noncareer deputy associate directors and one new associate director position that is noncareer. OMB's reorganization unit, which will help streamline the government, eventually will add about 30 new full-time jobs. Most will be political rather than career.

New Cabinet officers, anxious to get a handle on their agencies and get into the reorganization act also are eyeing the executive secretariat operations they inherited. Those offices, which can include several hundred people in a big agency, do everything from handle correspondence to program analysis, act as liaison with various bureaus and control the material that actually reach the secretary.

One technique for getting jobs shifted over from the career service to noncareer is to abolish or change them through internal reorganization. Commerce is in a flap because the Grade 14 head of its executive secretariat staff quit on May 13 after being advised that her job was overgraded and probably would be downgraded to a GS 11 or GS 9.

Commerce officials say that a proposed reorganization of the secretariat probably will result in the job being restored - after it is bumped down to a much lower level - back to Grade 14 with added duties. But it would be a Schedule C position. They say the 30-year employee, misunderstood her options, and they say they are planning to get in touch with her for another briefing that could result in her coming back to Commerce.

Other top-level reorganizations are in the works, and insiders anticipate many new Schedule C and NEA (noncareer executive assignment) positions will be layered into the upper reaches of the bureaucracy to make agencies more responsive to the wishes of the President and his appointees.

Inside Job: Justice Department types are looking for an employee who may have a sign fetish and nicotine-stained fingers. He (or she) has been removing "No Smoking" signs from the elevators at the Law Enforcement Assistance Administration.

Mandatory Retirement: Chairman Patricia Schroeder (D-Colo.) wants to know why the government, of all employees, has a mandatory policy requiring retirement at age 70. She plans a special one-day oversight hearing sometime next month before her House Employee Benefits subcommittee, and will work up legislation that would eliminate the 70-and-out regulation.

FBI Predicament: Former FBI assistant director William Cleveland is the May 13 luncheon speaker when the Association of Federal Investigators meets at the Fort McNair officers club. He will talk about the problems of FBI agents and officials now facing possible criminal charges for allegedly conducting unauthorized domestic spy operations during the 1950s and 1960s. Call 347-5500 for reservations.

Douglas Baldwin is the new consmer affairs and information boss at Interstate Commerce Commission. He is an ex-Capital Hill press aide and served with the old Office of Economic Opportunity and Interior.

Federal Women's Program Seminar: Civil Service Commission is sponsoring an all-day session July 13. It is aimed at equal employment specialists, personnel operatives and employees interested in the government women's program. Place is the Sheraton Park and the price is $30. Call 202 - 532-9772 for details.