The government is overpaying more than 150,000 of its white collar workers an estimated $280 million a year because their salaries and rank are not justified by the work they are doing according to a federal report to be released next month.

The Civil Service Commission study of white collar federal jobs in Grades 1 through 15 ($6,219 to $47,000) found widespread overgrading. But it also indicated that 45,000 other employes are not being paid enough for the work they do.

An outline of the CSC job study shows the greatest number of "overgradings" and overpayments to workers in middle and upper level jobs, with very little overgrading in beginning federal career occupations.

Members of the Classification and Compensation Society, a professional group of government workers whose job it is to set pay grades and standards, got a sneak preview of the CSC report at a special briefing yesterday. The section, held at the General Services Administration, was conducted by 'Marty Berman' of the CSC's powerful Bureau of Personnel Management and Evalvation.

Berman explained that the study - which took more than 18 months to conduct - is a random survey of 1 percent of all federal white collar jobs. CSC officials say this is the best, most accurate study ever made of the overall federal grade picture since it did not concentrate on trouble spots, or special occupations or limit itself to selected federal agencies.

Some reports by Congress have put the number of overgraded federal workers as high as 34 percent. But these studies were made in known "problem areas" rather than of the entire federal service.

Berman refused to go beyond the explanation he gave society members (complete with charts and graphs on slides). But he did give an interesting thumbnail sketch of the report that, if Congress and the White House take interest, could kick off a new round of tough agency grade adults that could lead to more job downgradings. Berman said the report, now being completed, will be released sometime in May. Meantime, some highlights from it.

Government-wide, the CSC study found that there was some kind of error or classification problem in about 17 percent of all white collar jobs.

10 percent of all the errors involved overgrading.

2.9 percent showed workers undergraded and underpaid.

The remaining 4.2 percent of the job errors involved problems with job titles and codes.

Cost of the overgrading to the government (after deductions were made for employes who are undergraded and underpaid) amounts to $279 million a year.

When Civil Service Commission investigators checked agency grade levels, they found a 10 percent error rate, whereas agencies policing themselves reported an error rate of only 5 percent.

CSC's report said that agencies had undergraded about 3 percent of their jobs while agency audits said the undergrading amounted to 1.5 percent of the jobs.

The biggest total error rate occured in jobs in Grade 10 ($16,618 to $21,604) where the entire 33 percent error rate was attributed to overgrading of job's report said the agencies had undergrade about 3 percent of their jobs while agency audits said the undergrading amounted to 1.5 percent of the jobs.

The biggest total error rate occured in jobs in Grade 10 ($16,618 to $21,604) where the entire 33 percent error rate was attributed to overgrading of jobs.

Nearly 13 percent of the jobs in Grade 4, the big clerk-steno, clerk-typist level, were overgraded, according to the CSC study.

Approximately 20 percent of the jobs surveyed in Grade 7, the level of senior secretaries and beginning professionals, were overgraded, according to the report.

Eighteen percent of the Grade 15 jobs ($36,171 to $47,025) were overgraded, as were 23 percent of the Grade 13 positions surveyed.

John D. R. Cole, head of the CSC bureau, said the grade study wax initiated by him after consulting with the "evaluation community." It was not ordered by the White House and is strictly "nonpolitical," Cole said.

When the survey becomes widely known, it should help President Carter's proposal to put a 55 percent limit on federal pay this year. Imagine a few headlines like: ONE BUREAUCRAT IN EVERY 10 OVERPAID. If the public and Congress get mad enough, federal workers might be "lucky" to get 5.5 percent.

Federal unions ought to be prepared to fight back, pointing out that the overgrading situations are generally the fault of agencies and many of the errors of long-standing.

Even so, the CSC report will not help the image of the federal worker in a year when civil servants need all the understanding they can get.