The Reagan administration, while reducing career civil service jobs at most domestic agencies, has "packed" the top ranks of the government with political appointees, the chairman of the Senate Governmental Affairs Committee said yesterday.

The leadership corps of the government, the Senior Executive Service, "has become politicized by the Reagan administration at the expense of the career service," Sen. John Glenn (D-Ohio) said.

The number of political appointees to the SES overall has grown 13 percent since 1980, while the number of career civil service members has dropped 5 percent, according to figures compiled by the General Accounting Office.

Nine departments or agencies have more than 20 percent political appointees in their top leadership groups, according to a Democratic staff study of the numbers. They are:

Education, 45 percent; International Development Cooperation Agency, which includes the Agency for International Development, 42 percent; Small Business Administration, 38 percent; State Department, 37 percent; Housing and Urban Development, 33 percent; U.S. Information Agency, 31 percent; Office of Personnel Management, 30 percent; Office of Management and Budget, 23 percent; Justice Department, 22 percent.

These figures include not only the SES but departmental executives such as Cabinet secretaries, who are political appointees in any administration.

Constance J. Horner, head of the Office of Personnel Management, responded, "It is irresponsible for the committee staff to be complaining that the administration is implementing a law passed by Congress."

She added, "The report fails to find a single instance in which federal agencies exceeded the authority granted by Congress" to make political appointments.

"Three of the five top managers here at the OPM central office and five of five of our regional directors are career civil servants," she noted.

Sen. William V. Roth Jr. (R-Del.), ranking minority member of the committee, said the staff's conclusions "seem to be the result of 'pick and choose' data -- pick the results you want and then choose the data to achieve them."

Roth said the report's reliance on percentages instead of numbers is "simply and grossly misleading."

"It is difficult to believe that increases of one noncareer SES appointee at the Small Business Administration {total employment, 4,906} and three noncareer SES appointees at Labor {total employment, 17,487} . . . are politicizing the federal government," Roth said.

Glenn said that although no legal violations were discovered, "disproportionate growth" in political appointments was found by the GAO, the investigative arm of Congress.

In the Agriculture Department, Glenn noted, the administration has cut the number of workers by 12 percent. But while the number of the department's career employes in the SES went down by 11 percent, political appointees to the SES increased 37 percent. Agriculture's "Schedule C" employes, who are usually special assistants to political appointees, increased 40 percent.

"The career SES is the institutional memory; it knows how to grease the wheels of government and make them turn," Glenn said.

The staff analysis of figures suggested that one president's replacement of career employes with political appointees can cripple a "successor's ability to effectively manage government."

Some agencies are close to the legal maximum of political appointees in the SES, which is 10 percent government-wide and 25 percent in an individual agency.

"The potential exists for the number of allocated positions to be inflated, thus increasing the number of noncareer personnel positions which would be allowed and still remain below the statutory limit," the staff report said.

The report said the departments of Education, Housing and Urban Development and State as well as the Small Business Administration and the U.S. Information Agency were bumping up against the statutory caps when total SES allocated positions were taken into account. The limits were exceeded when only currently "filled" jobs were counted, the report said.

Roth said the report failed to point out that the Reagan administration has reduced the number of allocated SES positions from 8,592 to 7,790. According to the GAO, 6,702 of these are filled.

The changes in the career-noncareer mix are striking in the agencies that govern the government -- OPM, the General Services Administration and the Office of Management and Budget, according to the staff report.

"Even small changes in the career-noncareer mix at the top of an agency can create a major change in operating culture," the report says.

"Notable by their absence {from lists showing growth in noncareer appointments} are the military agencies, which enjoyed growth in all categories of employes," it says.

Sally Marshall, GSA personnel director, said the statistics did not reflect the complete picture of the career-noncareer split at GSA and perhaps in other agencies.

In 1980, the base period for the study, the SES was new and many political appointees with some career service had recently joined it as career appointees. Because of this, she said, the number of individuals officially classified as political appointees was unnaturally low.

"I think the key issue is not whether these people are career or noncareer but whether these people are capable," said Mark Abramson, executive director of the Center for Excellence in Government, a group of former government executives. "It is a mistake to assume that political appointees are automatically not capable."