Mistakes made by the D.C. Department of Human Resources account overwhelmingly for the city's having the highest rate of erroneous Medicaid payments for the medically needy in the nation, according to Department of Health, Education and Welfare findings released today.

The HEW report, showing that 47.9 per cent of the District's payments in a six month survey period were erroneous, blamed DHR workers for 71 per cent of the mistakes, and recipients for 29 per cent.

Maryland's erroneous payment rate was 13.6 per cent. The state's agencies were blamed for 71 per cent of the mistakes, a level equal to the District's. The Virginia error rate was 7.1 per cent, and agency mistakes accounted for about 83 per cent of the total.

With nearly half its payments made in error, the District's wrongful payment rate was far above those in 43 states surveyed, as well as the national error rate of 9 per cent.

Medically needy persons are those who have incomes above the maximum to qualify for federal welfare programs, but too low to cover their medical expenses. The District has about 30,000 medically needy persons among its 160,000 Medicaid recipients. there are about 10 million medically needy people in the 25 million who receive Medicaid nationally.

Acting DHR director Albert Russo disclosed the District's error rate on Wednesday, but cited a slightly lower percentage -- 46.7 per cent -- in mistaken payments for the October, 1975, to March 1976, survey period.

HEW officials said their statistics came from a recheck of the sample claims studied by the District, and that the higher rate is more accurate.

Russo claimed that the District is unfairly compared in such studies to states rather than cities. State error rates include findings from rural and suburban areas that have lower densities of poor families, he said.

HEW has found, however, that most major cities have lower error rates than the District. Los Angeles had a rate of about 21 per cent and New York's was 19 per cent in the same survey, according to Victory Kugajevsky, HEW special initiatives director.

Russo also said he believed the mistakes resulted from both DHR and recipient failings, but were largely caused by understaffing in the agency.

Errors attributed to DHR in the report include failure to check out inconsistent information in clients' applications, and to verify claims according to its own policy.

Recipients' errors in the District were primarily caused by providing insufficient or incomplete information to the agency, the survey found. Only about 7 per cent of the claims sampled had errors that appeared to result from deliberately falsified information.

While the District had the highest error rate, many states had higher proportions of their mistakes blamed on the administering agencies. Seventeen states had higher percentages of agency errors, including two, Delaware and Iowa, whose rates were 100 per cent.

HEW officials said the survey, the first completed in a new medical eligibility quality control program will be conducted twice a year to find the rate of errors, the kind, and ways to eliminate them.