After a year of research, the District of Columbia has challenged a congressional study that indicated a much higher level of local government spending here than in 18 other cities of comparable population.

In a new report, the D.C. Office of Budget and Management System has concluded that many of the startingly high payroll statistics and spending figures cited last year by the Congressional Research Service (CRS) were unintentionally misleading.

And the D.C. report also contended that - in comparing governmental costs - it was not proper for CRS to mix two very different classes of cities.

In one class is Washington, with a dense but declining population. In the other class is, for example, San Diego, with a large land area and a growing population, requiring less police and fire protection and welfare services.

Such comparisons, the D.C. report asserted, "have no value for making decisions" on governmental policies.

"We have concluded that the CRS study represents an overly simplified treatment of a complex issue," Mayor Walter E. Washington wrote in a foreword to the new D.C. report. "Any judgement based on the CRS report inferring that the District's per capita expenditures are evidence of governmental inefficiency are unfounded."

The mayor said he agreed with CRS that more research, permitting better comparisons, is needed.

The CRS report was commissioned by Sen. Patrick J. Leahy (D-Vt.) and released in May 1977 as he opened his first hearings as the new chairman of the Senate D.C. Appropriations Subcommittee.

Because of those circumstances - and since Leahy embraced a conservative position on local finances - the CRS findings took on more than routine meaning for D.C. officials. In releasing their belated response, they made it clear that they wanted to counter any critical impressions left on taxpayers by CRS.

According to census data analyzed by CRS, D.C. spent $1,852 per capita in direct general expenditures in 1975, a figure 59 percent higher than an average of $1,163 for 18 other cities in the 500,000 to 1 million population range. Boston was second in spending with $1,652, and Baltimore, third with $1,510. Indianapolis ranked last with $816.

CRS said these figures averages in the money spent by state and county governments, in an attempt to make the figures comparable with D.C., which functions as a combined state-county-municipal govenrment.

The CRS report also said there were 709 local government employes per 10,000 population in Washington, compared with an average of 471 state and local employes in the 18 other cities.

The new D.C. analysis did not attempt to refute the CRS report on a point-by-point basis, but sought to show that the figures either were misleading or have only limited significance.

For example, when certain governmental functions are excluded (such as public housing and sewage treatment, which are often performed by special authorities), D.C. spending is only 8 percent higher than six older, dense cities with which it is more fairly compared. This contrasts with the CRS finding that overall D.C. costs were 59 percent higher than the 18 other cities.

Likewise, D.C. employment (with the same government functions excluded) was only 565 employes per 10,000 population rather than 709, only 3 percent above the average for the six older cities.

When employes of the D.C. prison system are excluded from the employment figures, the city report said, D.C. employment is slightly below that of Baltimore and only 6 percent above the average for the other older cities.

The District is the only city in the nation with a state-level prison system. Urban areas statistically have a higher proportion of criminals than rural areas located in states, the city report noted.

The D.C. report said cost comparisons cannot be made merely on the basis of total population, but on the proportion of the population served by various government functions.

For example, the report said, D.C. ranked second according to the CRS report in the amount of welfare spending per capita, but it ranked seventh in the amount of money spent for each person on the welfare rolls.

The D.C. report also found that Washington was the only city among nine studied that decreased its employment - by 8 percent - in the CRS study period. Indianapolis, the lowest-cost city in the study, increased its employment 9 percent in the same period.

According to the report, high living costs in an area will naturally result in high government costs, on a per capita basis, and Washington is one of the highest-cost areas. Moreover, city wages are influenced by the salaries paid by the federal and suburban governments.

An aide to Leahy said the senator would have no comment at this time on the city report. He said it had been sent to CRS for an analysis of the city findings.