A decade of inflation "has severely eroded" welfare payments to Virginia's neediest families, according to a new study that shows the average family receiving state aid gets only 38 percent of actual cost-of-living expenses.

The study, done by the firm of Ernst & Whinney for the General Assembly and the state's Department of Social Services, calls for increasing funding of the Aid to Dependent Children (ADC) program by about 30 percent and making sweeping revisions to update standards of need that have not been changed since 1974.

ADC, with an average caseload of about 60,000 families, is the state's major public assistance program. At least 80 percent of those families are made up of a mother and one or two children.

The study says that to fully meet Virginia's ADC needs, the program's annual budget of $70 million would have to be increased to almost $460 million, a figure the study maintains would be unrealistic to suggest.

Instead, the study recommends that an average family of three in an area where the cost of living is considered moderate receive $354 a month from ADC, an increase of $85 a month over current benefits.

Payments in Northern Virginia, considered a high-cost area, would be slightly higher under Virginia's system of designating low-, moderate- and high-cost areas depending on cost of living variations. The summary of the report released to the press did not say how much higher the Northern Virginia payments would be.

Since 1974, ADC benefits have risen 21 percent -- including a 5 percent increase effective last July -- while the official cost-of-living index has jumped 106.9 percent.

Even counting benefits from the federal Food Stamp program, fuel assistance and housing aid received by some of the families, the study found benefits "are significantly below the recommended standards of need for most" ADC recipients.

"This report the third in three years is respectable and reasonable and we see once again that our payment levels are grossly inadequate," said Deborah Oswalt, a poverty law attorney who is a consultant to the General Assembly. "One increase now won't solve all the problems. We can't afford the full need, but we can do better."

The Board of Social Services, which has acknowledged the need to revise Virginia's assistance program and oversees the social services department, is expected to make its recommendations to the General Assembly next month.

George M. Stoddart, press secretary to Gov. Charles S. Robb, said an increase in ADC payments is among many budget changes being recommended for Robb to present to the legislature. Robb proposed the 5 percent increase in ADC payments approved by the legislature last January.

Under current law, recipients of ADC aid are paid 90 percent of the standard of need based on the 1974 cost of living.

Under the study's recommendations, the standards would be brought up to date to reflect inflation and recipients would be paid 53 percent of those revised needs. That would amount to about a 30 percent increase in monthly benefits, a figure considered unlikely to be funded by the legislature.

According to social service officials, the department is reviewing suggestions by its own employes that the department could pay from its current level of funding as much as 41 percent of the revised needs.

Poverty officials suggested that this increase, along with additional funds from the legislature -- it is unclear how much will be requested -- would begin to reduce the gap between what the state now pays and actual living costs incurred by the state's neediest citizens.

Among the study's findings was that many ADC recipients are eligible for but do not receive food stamps, fuel bill assistance or housing aid.