A physicians' coalition, citing the "unprecedented threat to public health," today called for a moratorium on construction of nuclear power plants and a phase-out of those in operation.

The message was part of a full-page advertisement sponsored by more than 300 physicians, most from the northeast, in this month's edition of the New England Journal of Medicine.

The ad and a press conference here this evening marked the resurrection of Physicians for Social Responsibility, a group active in the early 1960s that publicized the dangers of nuclear fallout and urged an end to atmospheric nuclear weapons testing.

"We're playing with a very dangerous, threatening kind of pollution which is unique and which has no solution no matter what the safeguards," said Dr. Richard Feinbloom, director of the Family Health Care Program at Harvard Medical School and a past president of the orginization.

Added Dr. Herbert Abrams, professor and chairman of radiology at Harvard Medical School, "The risk of nuclear power is not wrth the economic benefits."

In a coincidence on the day after the Three Mile Island nuclear indicent, the physicians' and cites government figures stating that a major accident might cause 3,300 deaths, 45,000 injuries, billions of dollars in damage, 45,000 cancers over a period of years, and said it would "render an area the size of Pennsylvania contaminated and uninhabitable."