The oldest economic cliche in Washington is that the area is immune to recession because its biggest employer, the federal government, is a growth industry. In the past year, however, the "growth industry" has stopped growing and the prospect for 1982 is further retrenchment.

Federal workers make up about a quarter of the metropolitan area's labor force. In the past the security of their jobs and the steady growth of their ranks seemed as sure as death and taxes. But no longer.

In the 1960s, during the "Great Society" build-up under Lyndon Johnson, federal employment in the Washington area increased by 34 percent. In the 1970s, the growth continued, though at a slower rate, 14.3 percent. Now the growth has ended and a decline has begun.

According to figures compiled by private economists, there were 362,400 federal civilian employes in the Washington area in October 1980. By October 1981, the number had dropped to 353,000, and it is still going down as Reagan administration budgetary restrictions take effect.

Many of those reductions were achieved through retirement and attrition, but others were accomplished through firings--or reductions in force, in the government's euphemism.

Layoffs have occurred in the Community Services Administration, which was wiped out, in the Interior and Health and Human Services departments, and the Department of Energy, as well as in some regulatory agencies.

As the spending levels set by Congress in the 1982 continuing budget resolution begin to be felt, it is likely that some workers in the General Services Administration, the Office of Planning and Management, the Office of Management and Budget, and the Environmental Protection Agency will also lose their jobs, according to congressional analysts.

The actual numbers are hard to calculate because the 1982 federal budget is not yet final, some agencies may opt for furloughs instead of layoffs, and some workers will take other federal jobs at lower grades in their own agencies or in other departments.

Presidential counselor Edwin Meese, the No. 2 man in the Reagan White House, said last week that "a lot of the work force that will be cut will be outside the Washington area" in regional and district offices. The administration, he said, would work with local governments here to mitigate the effect of the cuts, and hopes that economic recovery in the private sector will offset some of the impact of the federal layoffs.

The overall effect, for the first time in decades, has been to put federal workers among those who have doubts about long-term job security. Combined with similar reductions by another major employer--the District of Columbia government--they put an unfamiliar cloud over the capital region's economy.

Those who have lost federal jobs represent only a small fraction of the Washington area's labor force, but the impact on the local economy goes beyond their numbers, economists believe.

The effect appears to be at least partly psychological, as workers still employed feel insecure enough to postpone purchases and defer commitments.

"Here in Washington, the basic theme always was that we were recession-proof because of federal employment," said James Cotter, an economist for the Chesapeake and Potomac Telephone Co. "The fact that the numbers have gone down at all is the big thing, because we always counted on it to be inching upward over the years. The impact is more of a lack of growth than of an actual downturn."

"There is a very great sense of frustration among the workers, even those whose jobs are secure--if any are," said a spokesman for the American Federation of Goverment Employes. "The uncertainty about their professional life carries over into uncertainty about their personal life."

The federal government is not the only public body reducing its payroll. According to the U.S. Bureau of Labor Statistics, the total number of people in federal, state, county and municipal employment throughout the nation dropped last year for the first time since World War II.

The number of public employes declined by about 316,000, of whom about 40,000 were federal employes. There are still about 16 million public workers, but economists around the nation say the reductions have eliminated a shield that had deflected some of the impact of previous recessions.

According to a congressional task force headed by Rep. Michael Barnes (D-Md.), a total of 11,845 federal workers were laid off in the 1981 fiscal year and the start of fiscal 1982, and at least 5,400 more will lose their jobs by the end of this year.

In addition, some federal agencies, facing reduced allocations, are planning to place some employes on extended furlough.

When Congress enacts the final 1982 appropriations bills next month, superseding the interim resolutions adopted in early December, some allocations to individual departments could be increased. But over the next two years the prospect is for further reductions, some of them abrupt and painful, as the administration tries to eliminate 75,000 nondefense jobs.

At the same time, executives of consulting and placement firms say reductions in government contracts to consultants and suppliers have undercut the usual parallel job market.

According to Pat Court, spokesman for the federal Office of Personnel Management, the work-force reduction will not be felt equally by all departments or all types of workers. There is no overall federal hiring freeze, he said, and prospective employes with some special qualifications can still be added to the payroll.

"If you have a master's degree in electrical engineering," he said, "we can very much use your services. If you're a grants specialist--sorry, we can't use you."