Retired admiral Elmo R. Zumwalt Jr. yesterday accused government and industry scientists of manipulating research data to hide what he called clear evidence that Agent Orange may have caused cancers, birth defects and a wide variety of other ailments in Americans who fought in Southeast Asia and their offspring.

The admiral, who recently reviewed studies on the widely used defoliant for the Department of Veterans' Affairs, charged that the distortions continue to "needlessly muddle the debate" over the impact of dioxin-laden chemicals on the American public. Forms of dioxins, a carcinogenic agent in Agent Orange, are present in herbicides widely used in American agriculture.

Zumwalt, a former chief of naval operations, last month urged the VA to declare that Agent Orange is the suspected cause of 28 ailments, a list much longer than any scientific panel has recommended. At that time, the admiral also assailed a VA committee that has been reviewing research papers on the chemical's impact, saying it had been too slow to recognize "there is more than enough verifiable, credible evidence" to link the suspected illnesses with exposure to the chemical.

Yesterday, appearing before the House Government Operations subcommittee on human resources and intergovernmental relations, Zumwalt went further.

He first noted that he had suspected that his son, a former naval officer, died of cancers caused by Agent Orange. But Zumwalt said that until recently he had also believed "that there was insufficient scientific evidence to support a linkage between his illness and Agent Orange exposure. That was, of course, the conventional propaganda.

"The sad truth which emerges from my work is not only is there credible evidence linking certain cancers and other illnesses with Agent Orange, but that government and industry officials credited with examining such linkage intentionally manipulated or withheld compelling information of the adverse health effects . . . . "

Although Zumwalt's position is not shared by all researchers, his testimony is certain to be used by veterans groups and their advocates in an effort to keep the issue alive on Capitol Hill.

Yesterday Zumwalt singled out Dr. Vernon Houk, a former member of a White House Agent Orange Working Group and now a senior official at the Centers for Disease Control in Atlanta, a federal agency that has conducted several major studies into use of the herbicide.

"I believe that Dr. Vernon Houk . . . has made it his mission to manipulate and prevent the true facts from being determined," Zumwalt charged. He said the CDC's Agent Orange studies, which Houk supervised, and a similar Air Force study were "absolutely without merit."

A spokesman for the CDC declined comment, but an Air Force spokewoman rejected charges by Zumwalt and the subcommittee that its study had been suppressed because it suggested a link between birth defects and exposure to the defoliant.

Patty Turner, a spokeswoman for the Air Force Surgeon General, said the 1984 study of Air Force personnel was never released because a panel headed by an official of the National Cancer Institute found it was "scientifically flawed." A more detailed study of the health of personnel who sprayed the chemical during the Vietnam conflict will be released "early next year," she said.