The National Wildlife Federation yesterday accused the Interior Department of suppressing a film that encourages hunters to use steel shot in their shotguns instead of lead shot.

The 30-minute film, "Field Testing Steel Shot," was produced during the Carter administration after environmentalists and government experts expressed concern that waterfowl were being killed by shots that missed. Bottom-feeding birds ingest the lead pellets with their food and are poisoned by them.

Environmentalists noted that the birds eat steel pellets, too, but the steel ones don't break down in the birds' bodies. However, many hunters prefer lead shot because the pellets are heavier and more likely to kill rather than cripple the bird. Many also believe the softer lead pellets are less damaging to gun barrels.

Alan Levitt, a spokesman for the department's Fish and Wildlife Service, said the $28,500 film was "poorly produced," is not a finished product and has not been released for public viewing. It "doesn't accurately portray the steel shot issue," he said.

The wildlife federation charged that an Interior aide recently asked executive vice president Jay D. Hair to turn over the federation's videotape of the film. Nothing doing, said Hair, who said the group will continue to show it.