The Veterans Administation has delayed its study of the defoliant Agent Orange unnecessarily and has undermined efforts by the Army to get the long-awaited effort started, the head of the congressional Office of Technology Assessment says.

At the same time, 101 House members led by Rep. Thomas A. Daschle (D-S.D.) have called on the VA to turn over the study to the federal Centers for Disease Control because the VA has lost its credibility among Vietnam veterans.

VA officials maintain that they are not delaying the study, but are proceeding as fast as possible with caution because its results could cost the government millions of dollars in compensation to disabled veterans.

Three years ago, Congress ordered the VA to determine whether exposure to Agent Orange, which was widely used during the Vietnam war, damaged the health of veterans and their offspring.

Veterans claim the defoliant has caused cancers, nerve, liver and kidney disorders, tingling in their fingers, skin conditions, numbness, vision and hearing impairments, fatigue, reduced sexual drive, impotence, miscarriages in their wives and birth defects in their children.

Earlier this year, Congress ordered the VA to give priority treatment to veterans with disorders suspected of being caused by Agent Orange. But the agency has refused to pay any benefits because it maintains there is no scientific proof that the spray causes health problems.

The Office of Technology Assessment has the responsibility for approving the structure of the Agent Orange study and monitoring it. But in a recent letter to the Senate Veterans' Affairs Committee, John H. Gibbons, the director of OTA, outlined several ways in which the VA had delayed the investigation.

Among other things, Gibbons said the VA has delayed the study by asking numerous government scientific panels to review its study plans. The study can't begin until the agency sets its parameters, Gibbons explained.

Originally, the VA said it would compare the health of two groups, Vietnam veterans exposed to Agent Orange and those who weren't. But this spring it announced it might add a third group, GIs who were not in Vietnam but who were in the military during the Vietnam era.

VA officials said they are waiting for a report from the National Academy of Sciences before making a decision on how to structure the study, but Gibbons noted that the agency already has received opinions from three other scientific groups. "Waiting on still another technical review . . . seems unnecessary and can be viewed as a delaying tactic," he said.

Gibbons said the VA also rejected an attempt by the Army to speed things up. In April, the Army began searching its records to identify 1,800 Vietnam veterans who would fit into the three study groups, but the VA refused to cooperate.

The failure of the VA to make decisions has led to a "blurring of lines of responsibility" between groups trying to study the defoliant, Gibbons added.