President Carter's efforts to overhaul the antiquated civil service system have gotten well-timed reinforcement from a nonpartisan group of business leaders with experience in high government posts.

In announcing proposals that parallel those the president is expected to send to Congress next week, the Committee for Economic Development suggested that unprecedented public concern over the size, cost and responsiveness of government makes the time "ripe" for long-needed changes.

The committee recommends measures that will strengthen authority and flexibility of federal managers in the way they hire, promote, fire and otherwise handle employes. As well they are aimed at providing more effective protection of civil servants from political abuse.

BAsed on "in-depth research" as well as ideas that have "evolved over the past 35 years," as one spokesman put it, the CED proposes, among other things, abolishing the Civil Service Commission.

In its place there should be two separate entities to handle the commission's often conflicting responsibilities -- one for federal personnel management and another for protecting employes' rights and the merit principles on which the system is founded, CED said.

Under the current system of inadequate authority for managers and insufficient protection for employes CED said, "We are suffering the worst of both worlds."

The group also recommends creation of a senior executive service to increase incentives, as well as risks, for managers, and a number of other changes in personnel policies and practices to improve performance and productivity of government services.

In one departure from the Carter administration program, CED expressed concern about so-called special emphasis hiring plans designed to place women and minority group members into a "certain proportion" of job vacancies, "if they use any criteria other than merit . . ."

Civil Service Commission Chairman Alan K. Campbell, a chief administration "salesman" for change, said he was "delighted" with the CED statement, which "parallels closely" the president's planned recommendations. As for the question of special emphasis hiring plans, Campbell added that "there is no substantial disagreement there because we intend to use selection procedures (in any such special plan) consistent with merit principles."

Franklin A. Lindsay, chairman of the CED program committee that prepared the statement, served in high-level posts under the Eisenhower and Johnson administrations, heading the President's Task Force on Organization of the Executive Branch in 1869-69. He is chairman of Itek Corp.