A simple, cheap contraceptive device called the cervical cap is being suppressed by the Food and Drug Administration, though it has been successfully used in Europe for 140 years, a spokeswoman for women's health groups charged yesterday.

The cap -- a plastic or rubber device fitted to the cervix or tip of the womb -- is being used nonetheless by a growing number of American women who fear the possible ill effects of the birth control pill, Barbara Seaman, a New York writer and cofounder of the National Women's Health Network, told a Senate health subcommittee.

In an interview later yesterday, Dr. Gabriel Bialy, chief of the contraceptive development branch at the government's National Institutes of Health, said there is indeed a "rivival of interest" in this age-old device, and NIH's National Institute of Child Health and Human Development hopes to finance studies of its safety and effectiveness.

Researchers affiliated with two universities, Harvard and Chicago, said they are conducting new tests of the cap and are optimistic about its future as an alternative for women seeking a safer contraceptive.

All this interest centers on a thimble-shaped device first used in ancient Sumeria. The modern version was perfected in Germany in 1838. Women's health groups have been importing a version made in Great Britain.

This, said Seamen, has prompted FDA to seize some shipments.

Also, FDA has formally proposed to prohibit any American marketing of the cap since its effectiveness and safety have never been proved here. An FDA medical advisory panel said defective caps might cause injuries.

After Seaman's testimony, however, Dr. Lillian Yin of FDA's Bureau of Medical Devices told Seaman she agreed with her that the cap is "as safe as" the widely used diaphragm. Both the cap and the diaphragm act as barriers to sperm, but the diaphragm usually has to be removed after use, while many women keep the cap in place for a month at a time.

However, said Yin, U.S. law requires the medical devices, like prescription drugs, be backed by studies.

The problem, Seaman testified, is that drug firms aren't interested in the cap because it is too cheap to promise a profit.

Dr. James Koch, Harvard research associate at Boston Hospital for Women, agreed. He has placed British caps in 350 women. The women take them out themselves and reinsert them every seven days, adding in the case of this study, a sperm-killing material. Some of these women have used the caps as long as 20 months.

There have been few problems except for "a few" pregnancies, Koch said. But current caps are far from perfect, he added, and he had associates are working on a way to make better ones available in many shapes and sizes, for better fit.

Dr. Robert Goepp of the University of Chicago said he and Dr. Ewe Freese are custom-making caps after making a model of each patient's cervix, and 30 women are wearing their latest devices "with no detectable problems."

Goepp said there is commercial interest in making his device and he believes it could be made and fitted cheaply enough to permit wide use.

The main problem here and in other women's health matters, said Senate Health Subcommittee Chairman Edward M. Kennedy (D-Mass.), is that women have long been "second-class citizens" whose true medical needs have been slighted.

Other witnesses -- poor, elderly, widowed and divorced women -- told the subcommittee how they remain uncovered or poorly covered by health insurance, while forced to live in poverty to pay doctor bills.

Eleanor Smeal, president of the National Organization for Women, urged laws to guarantee care and research in many areas, including reproduction and childbirth. CAPTION: Picture, Seaman, with Health Research Group's Sidney Wolfe, testifies on British device. By James K. W. Atherton -- The Washington Post