Although the career staff at the Office of Personnel Management has shrunk from 8,000 to less than 6,000 in the past four years, the number of political appointees in the agency -- the watchdog of the federal merit system -- has jumped from 17 to 48 since the Reagan administration took office.

OPM is one of a number of agencies that eliminated career jobs, through layoffs and attrition, but added political appointees to give political bosses greater control.

The number of political appointees at the Office of Management and Budget, which polices federal program dollars and jobs for the White House, grew from 32 to 48 during the four-year period.

The names of incumbent political aides, from presidential appointees to confidential secretaries and chauffeurs, are contained in the "plum book." That quadrennial political best seller is due to hit government bookstores tomorrow morning.

The book, rarely called by its correct title of "Policy and Supporting Positions," is a patronage hunter's dream guide to federal employment opportunities. Copies, usually snapped up quickly at Government Printing Office bookstores, will be going for around $9 this year.

This year's plum book is 101 pages fatter than the book listing patronage jobs in the Carter administration that four years ago was turned over to the incoming Reagan administration.

One reason the book is larger is that this issue contains a listing of more than 6,000 career jobs in the Senior Executive Service. That is the elite corps of federal executives, paid from $61,000 to $72,000, created by the Carter administration to give political officials more flexibility in making government job assignments. Most of the career executives work here.

Although only about 10 percent of the overall SES work force can be staffed by political appointees, agency heads have wide leeway within that framework to move or transfer career executives or replace them with political appointees. That has been done with a vengeance in many departments and agencies.

The number of noncareer appointees in the politically supercharged Department of Energy, for example rose from 116 to 136 during the four-year period, while overall employment dropped nearly 4,000 jobs.

Career members of the SES are not listed by name in the new plum book, but their jobs, titles and locations are spelled out -- something that has made many of the careerists nervous.

The Senate Governmental Affairs Committee prepared the book this year. In a bipartisan decision, it authorized listing the career SES personnel provided their names were not used.