A construction ditch that caved in and killed a worker last month had no wall support as required by Virginia regulations, Fairfax County and state officials said yesterday.

The construction death was the first since the Reagan administration allowed Virginia to assume responsibility for construction safety inspections last October. It has revived a debate in Fairfax, which first erupted in 1979 after a series of construction deaths, over whether Virginia has the will and the resources adequately to police building safety.

"Their attitude has always been to worry more about the contractor than the individual," said County Supervisor Audrey Moore, who was critical of the federal decision to pull out of Virginia. "I think the state office was determined to undo what the feds had done."

The trench that caved in on April 16 was at the construction site of a laundry and dry cleaning plant in Fullerton Industrial Park, according to county officials. More than two feet of dirt slid into the 7-foot-8-inch deep trench. The worker, Karl E. Allen, 32, was knocked over and his neck broken.

A Fairfax County inspector, Jim Lowery, also said yesterday he had noticed an unsupported ditch in another part of the same construction site the day before the fatal accident. He ordered the supervisor to shore up the ditch before anyone else walked in it, Lowery said, and the supervisor promised to comply.

The trench "appeared to be neither sloped nor shored" although it was deep enough to require one or the other safety measure, according to a memorandum from Larry R. Coons, county director of environmental management.

County officials identified H. Manny Holtz Inc. of Wheaton as the company in charge of the laundry plant construction. The president of the company, Manny Holtz, yesterday declined comment.

The director of Virginia's occupational safety division said he expects to take action in the cave-in in a few days. The agency could impose a fine of up to $1,000.

Virginia had tried since the early 1970s to establish control over safety inspections at construction sites, but federal officials consistently found weaknesses in the state operation. When two 25-year-old workers were buried to death in a well publicized ditch collapse in 1978, the county board asked the federal government to increase its inspection efforts and train local inspectors to look for potential hazards.

Several months after Reagan took office, the Occupational Safety and Health Administration pledged to transfer control, a move that delighted the Republican administration of then-Gov. John N. Dalton. Federal inspectors were withdrawn and the five-person state force in Northern Virginia was not augmented.

Clayton P. Deane, assistant to the Virginia commissioner of labor and industry, said state control already has reduced red tape of competing bureaucracies without reducing safety.

County officials said that state inspectors are more responsive than they were several years ago. In addition, more than 100 Fairfax inspectors are now trained to act as what Wicker called "the eyes and ears" of the state inspectors.

"We've got a more concentrated job safety presence than anywhere else in the United States," said Richard E. Lawson, deputy director of inspections for the county. "And the contractors know that."

Still, Moore said she fears the cave-in last month may signal a relaxation by contractors now that federal inspectors have left the area. "When the federal people were in here, they were very tough," she said. "I don't know if this is a sign we've got a bad situation going on or not."