An environmentalist accused Virginia officials last night of embarking on "an ill-conceived . . . wrong-headed program" to dump low-level nuclear wastes at a site in the state by the mid-1980s.

Speaking at a public hearing in Alexandria, Fred Millard, a member of the environmental group Potomac Alliance, said state officials are ignoring recent federal studies backing disposal of such low-level wastes at the sites where they are created rather than shipping them to a dumping site. Millard said the Virginia officials are rushing "pell mell into a subject plagues with problems" without adequate information.

Robert F. Testin, chairman of the Virginia Solid Waste Commission, declined to respond to Millard's statements, saying the commission was only gathering information at hearings such as the one held last night.

Virginia must soon decide how to dispose of radioactive materials left over from nuclear power plant activity and used by hospitals and industries because current dump sites for the waste outside the state are being closed.

Those sites, located in South Carolina, Nevada and Washington State, have experienced problems such as leakage of low level nuclear material into the soil and faulty record keeping by officials, Millard and the officials agreed.

State Sen. Wiley F. Mitchell Jr. (R-Alexandria) defended the state's search for a single site, saying that keeping wastes at a variety of locations would be "appalling." Such a practice would create "hundreds of locations where there was little control or supervision . . . and would create the potential for an environmental disaster," he claimed.

Low level nuclear wastes include such items as clothing and plastic containers contaminated by exposure to nuclear material and needles and equipment used in certain kinds of medicine. Officials claim people can be harmed only by long term exposure to radiation from these materials.

Millard and Mitchell spoke at a work session sponsored by the Solid Waste Commission and the Virginia Department of Health. The two bodies have been granted $300,000 by the legislation to determine if there are sites large enough in Virginia for the permanent dumping of low level nuclear waste. They expect to issue a report on their findings to Gov. John N. Dalton withing 18 months.