The D.C. Rental Accommodations Commission adopted a controversial report last night that will allow thousands of tenants in the city to get either rent refunds or lower-than-expected rent increases this spring as a result of overcharges inadvertently allowed last year.

The overcharges resulted from errors in a 1978 report prepared for the commission and the D.C. City Council last year by a special staff, and were not the fault of landlords.

According to the new report, thousands of tenants may have been overcharged because of errors in determining operating cost increases for the city's landlords.

Under the city's rent control law the rent commission is required to report to the City Council every year on the state of rental housing, and decide whether landlords should be allowed rent increaes, and how much they should be.

By law the increase cannot exceed the change in the Consumer Price index for the previous year. Landlords are allowed the increases based on a formula that reflects operating costs of their buildings.

The report adopted last night sets a 10.7 percent maximum rate for automatic rent raises this year. Commission members said last night, however, that a consensus appears to have been reached that will require all landlords who overcharged tenants by more than $10 a month last year to refund that money before any increase can be taken this year.

One source has estimated that some tenants may have been overcharged up to $15 a month because of errors in the 1978 report.

Last night's report was adopted by a 3-to-2 vote. Marie Nahikian, Judy Walton and Chineeta McGuire -- all tenant representatives on the nine-member commission -- voted in favor. Patricia Wells, a landlord member, and Richard Streeter, a public member and commission vice chairman, voted against adoption.

Streeter, an attorney, said after the meeting that he feels the report is "basically wrong." It's going to wipe out a substantial number of smaller and poorer landlords," Streeter added.

A spokesman for the landlords association has estimated that most of the owners of the estimated 112,000 rent-controlled apartments in the city may be adversely affected at a time when operating costs have skyrocketed.