A group of business, labor and government leaders gave its support today to eliminating the earnings test for Social Security recipients as a way of alleviating the manpower shortage expected at the end of this century.

Current law prevents retirees from earning more than $5,500 a year without sacrificing some of their benefits. The increased cost to the Social Security system of eliminating the earnings test would be offset partially by these employes' continued Social Security payments and by economic growth, the group contended. President Reagan endorsed this idea during his campaign. A Ways and Means subcommittee is now considering removal of the test for retirees over 68 years old.

This was one of the recommendations made during a three-day symposium just concluded on the future of older workers in America, sponsored by the Work in America Institute. This nonprofit organization, established in 1975 and funded by industry and foundation grants, is devoted to advancing productivity and the quality of working life.

The conference was held at Arden House, a mountaintop retreat north of New York City built in 1906 by railroad magnate Edward Henry Harriman and donated to Columbia University in 1950.

Another recommendation was for a government study of the effects of portable pensions on productivity costs and how to administer them. Only one-third of retirees receive a private pension, partly because many workers do not stay on one job long enough to earn a vested interested in the plan. Federal law requires vesting no later than after 10 years. This issue was raised when the Pension Reform Act was passed in 1974. But because of its complexity, suspected cost; an opposition from some segments of business and labor, it was dropped.

The conferees also passed a number of more general resolutions calling on employers to support age-neutral practices and policies, career counseling, preretirement programs, expanded work opportunities in later life, and employment opportunities such as sabaticals, in-house training and tuition assistance designed to help workers make career changes.

They shied away, however, from deciding on how to reach those goals. A recommendation to modify the existing practice of "stretching out" pay raises for long-term employes, who are likely to be older workers, failed to pass. So did a recommendation that employers examine the options of flexible work locations (primarily the home) for all employes. Ideas such as advocating full benefits accrual after age 65 were considered too controversial to get beyond the suggestion stage in workshops.

Donald K. De Ward of Travellers Insurance Co. spoke about the plan his firm recently put into effect in which retired employes may register at a job bank for temporary jobs with the company for as many as 960 hours a year, equal to about half a year's full-time work, without losing any pension rights.