Public employes, especially beleaguered federal workers, held their own pep rally yesterday, touting their services and lashing out at their image in some circles as lazy, overpaid bureaucrats.

"Persons running for the highest office in our land have run against the career public servant . . . . Of course it undermines morale, of course it drives people out of government, and of course it makes it difficult to recruit," complained Arthur Flemming, former chairman of the U.S. Commission on Civil Rights and now president of the National Council on Aging.

Flemming, addressing about 500 employes who gathered at the D.C. Convention Center to commemorate the 100-year-old U.S. civil service system, said federal, state and local workers should start demanding more respect and protection from elected officials.

He suggested that they pressure the Republican and Democratic parties to adopt platform planks that pay tribute to and acknowledge the importance of public employes' contributions.

"Keep the candidates' feet to the fire," Flemming urged.

The rally, organized by the Public Employees Roundtable, a 26-group coalition of public employe advocates, featured government, union and business officials as well as prominent public employes. Also on hand was Donald J. Devine, director of the Office of Personnel Management and the architect of health benefit and management reorganization plans that have infuriated many federal workers.

"We don't always agree on everything," said Devine, whose introduction was greeted with scattered boos. But he told the crowd that he, too, believes there is a "need to dispel this bad rap that public employes aren't good workers."

Congress and President Reagan have proclaimed Jan. 17 as Public Employes Appreciation Day, and organizers of the rally had hoped that Reagan, Vice President Bush or some other well-known White House official would address the gathering. The administration, however, dispatched Ralph Bledsoe, special assistant in the Office of Policy Development, who sat on the dais but did not speak.

"It's a slap in the face to federal workers," one union official said later.

While Devine tried to be conciliatory in his remarks, most of the other speakers were anything but.

"I'm not sure a day is going to be enough to undo all the degradation and abuse," said Rep. Patricia Schroeder (D-Colo.), who said the government "can't expect public employes to be productive, and then hit them every day."

Kenneth Blaylock, president of the American Federation of Government Employees, said public employes have "very little to celebrate" because of the way they "are being maligned and alienated."

Former Iran hostage L. Bruce Laingen, now vice president of the Naval War College, said he wanted to salute the crowd and the nation's 16 million public employes as "unsung heroes." He said confidence in public employes had declined because some "would use us as a favorite whipping boy," and he called on the employes to assert more "moral and personal discipline" to make the bureaucracy "worthy of what this great democracy expects of us."

Other speakers included Sen. John W. Warner (R-Va.); D.C. Mayor Marion Barry; John J. Byrne, board chairman of GEICO Corp.; Dr. Frances O. Kelsey, an official with the National Center for Drugs and Biologics who held up the sale of thalidomide here in the 1960s, and Major David C. Hilmers, a NASA astronaut.