WASHINGTON (AP) _ A study on exposure to Agent Orange, the toxic defoliant used in Vietnam, may have been designed by the government to fail, a congressman charges.

Rep. Ted Weiss, D-N.Y., also said Tuesday the decision two years ago to cancel the massive study by the Centers for Disease Control has wrongfully put the lid on other government research.

''The federal government has effectively used the CDC study to stifle any attempts to link Agent Orange to health effects,'' Weiss said at a hearing of his Government Operations subcommittee on human resources and intergovernmental relations. ''CDC has had the last word on Agent Orange.''

''Either it was a politically rigged operation or it was a monumentally bungled operation,'' Weiss said.

Dr. Vernon N. Houk of the CDC said the study was abandoned because the CDC couldn't find the right data to develop a valid method to study the health effects of the defoliant.

But several other scientists, including former CDC researcher Dr. Dennis M. Smith, testified that the needed data, including detailed troop movement, were available from the Defense Department's Environmental Study Group.

Houk, chairman of a scientific panel of the White House Agent Orange Working Group, denied suggestions by Weiss that the White House called the shots on the study.

''The science panel was not considered and is not considered and has never functioned as a political entity,'' he said.

Weiss said CDC conducted another study finding a low sperm count and malformed sperm among Vietnam veterans. As a result of the earlier study, CDC dismissed any link between those findings and Agent Orange because ''we found that few Army ground troops were heavily exposed to dioxin-containing herbicides,'' Weiss said, quoting the report.

Many Vietnam veterans have said they have developed cancer and that their children have a high incidence of birth defects because of Agent Orange, which was used to clear dense jungle during the war.

There are 34,000 veterans seeking government benefits as a result of disabilities they say were caused by Agent Orange. The active ingredient of Agent Orange is dioxin, a cancer-causing chemical.

The Veterans Affairs Department, formerly the Veterans Administration, said in May it would take another look at those cases.

Veterans exposed to Agent Orange also have sued the seven chemical companies that made the herbicide. The suit was settled, and an Agent Orange fund was created to pay $180 million in damages. Caretakers for the fund say $12 million has been distributed to 6,039 veterans and 13 organizations so far.