The Reagan administration's contention that low job turnover in government proves that workers are overpaid is a "propaganda stunt" based on misleading data, Rep. William C. Ford (D-Mich.), chairman of the House Post Office and Civil Service Committee, charged yesterday.

Ford zeroed in on a study by the Office of Personnel Management comparing "quit rates" (the percentage of employes who voluntarily leave to seek other employment) in the federal government and private industry.

OPM said it found that the private sector has a quit rate more than three times higher than the government's, and concluded that higher pay in government was the reason. The government quit rate is 3.8 percent, compared with about 13 percent in the private sector, OPM said.

OPM administrators said the turnover data justified the proposal to cut federal pay 5 percent next year and withhold raises until industry pay catches up with the government. Federal unions have challenged OPM's data, saying it is stale and has been misinterpreted.

Ford accused political officials of the OPM of trying to pass off the turnover data, which is part of a much larger report on compensation, as the work of its career service staff. The chairman said that the quit rate section was actually written by Patrick J. Korten, a top aide to agency director Donald J. Devine.

The portions of the report assigned to career OPM staffers was used as "boilerplate," Ford said, while Korten, a former radio reporter here, kept the job turnover portion of the report to himself and added it after the career employes had completed their sections.

Korten said yesterday that the career experts were involved in drafting the entire report. "Any way you slice it, any set of numbers you care to examine shows the same thing, that the government quit rate is significantly lower than it is in the private sector," said Korten, an executive assistant director in the agency.

The committee chairman, a staunch backer of labor unions and federal workers, said that OPM used selective data to make the industry quit rate higher, and make the government's appear lower.

He said, for example, that OPM considered only actual resignations by government employes, but used data that also included retirements and deaths in private industry. The effect, he said, was to make it appear that turnover is much higher in industry than in the government.

Korten said yesterday that OPM did not, as the committee said, use data on retirements or deaths in its quit rate report. "We compared apples to apples," he said.