One of the medical world's most respected figures yesterday urged American doctors to divest themselves of their increasing ownership of protfit-making medical business earning billions of dollars.

The American Medical Association should declare it unethical for a doctor to derive any income from health care except fees for his services, said Dr. Arnold Relman, editor of the New England Journal of Medicine.

Doctors, Relman pointed out, have become an important part of the ownership of for-profit hospitals, nursing homes, kidney dialysis businesses, laboratories, pain clinics and many other health firms. Perhaps a third of the $240-billion-a-year American health care industry is in private hands.

Both this money-making "medical-industrial complex" and doctors' financial participation in it are growing, Relman said, and unless doctors give it up, the public will lose confidence in them as honest, disinterested representatives of their patients' best interests.

Moreover, he said, doctors will be lending themselves to a new "vested interest" that could become the "largest, richest and most influential" lobby affecting the nation's laws. Already, he said, the doctor-controlled private kidney dialysis industry has blunted the force of a new law that could have moved thousands of patients from private clinics to cheaper home dialysis.

As another example of a potential conflict between a doctor's financial interest and his patient's welfare, Relman quoted a brochure published by Brookwood Health Services of Birmingham, Al., one of many corporations that operate investor-owned hospitals. The firm, the brochure said, "views each physician as a business partner," and to this end, Relman said, it "recruits young physicians and subsidizes their start."

Relman made his plea in the current issue of the weekly journal he edits. The New England Journal is far and away the nation's most highly regarded medical publication and one that has increasingly become American medicine's strongest moral voice.

AMA officials maintained yesterday that all but a few doctors continue to put their patients' welfare ahead of their own pocketbooks, whether or not they own any share in businesses that also serve their patients. wDr. James Todd, an AMA trustee, said every physician-patient relationship has a potential, "built-in conflict of interest," because every practitioner earns his living caring for patients, but "it has always been our principle that the patient's welfare comes before economics."

Relman conceded this point, but maintained that the role of thousands of doctors in health profit-making has grown far beyond that once simple relationship.

Todd defended doctors who have ownership shares in health enterprises, including stock ownership in drug and health supply companies.

But he said he, too, could "see great harm in a physician opening his own hospital" or nursing home if he also admits patients there, because "he shouldn't be on both sides of the fence."

But in general, he said, a new AMA ethics code, adopted in July, prevents real, "not some hypothetical," harm to patients by saying that all doctors "shall be dedicated to providing competent medical service," that they "shall deal honestly with patients" and "strive to expose" doctors "deficient in character or competence, or who engage in fraud and deception."

AMA prohibition of ownership of health business would be impractical and probably illegal, said Bruce Nortel, attorney for the AMA's Judicial Council. He said the courts, the Federal Trade Commission and legislatures have forced the AMA and local medical societies to be much more lenient in permitting doctors to advertise their services and participate in profit-making medical businesses.

Relman said he knows the AMA might not be able to make a new ethical prohibition of medical business activity stick, and might face antitrust action if it tried.

"Yet," he argued, "I believed that the risk to the reputation and self-esteem of the profession will be much greater if organized medicine fails to act decisively in separating physicians from the private exploitation of health care."