The nation's doctors were warned yesterday of probable "strenuous, strict controls within the next two years" to hold down their payments from Medicare.

"Congress is going to be pushed to do something drastic" to contain soaring Medicare premiums, said Chairman Fortney H. (Pete) Stark (D-Calif.) of the House Ways and Means health subcommittee.

Stark's warning came at a committee hearing where Medicare administrator William L. Roper testified that the 38 percent leap in the Medicare premium published in the Federal Register yesterday was largely the result of a continuing increase in Medicare payments to doctors.

The main reason, Roper said, was a rising volume of services per patient that, in some cases, were "clearly inappropriate" or "questionable."

The premium paid by persons enrolled in the Medicare program will rise from $17.90 a month this year to $24.80 a month in 1988, the biggest jump in the program's history.

Stark and Ways and Means Chairman Dan Rostenkowski (D-Ill.) said it appeared that Roper's calculations for the 1988 premium increase were valid based on program costs. Stark said he did not believe much could be done to roll back the increase, indicating that the bigger issue is how to contain future payments to physicians.

Medicare hospital benefits (Part A) are financed by the Social Security payroll tax. But doctor bills and some related payments (Part B) are paid for by the enrollee premium (25 percent) and by Treasury general revenues (75 percent).

In recent years, Medicare physician spending has been rising about 13.5 percent a year per aged enrollee, far outstripping the inflation rate. Part B, overall, has been rising about 17 percent annually over the past five years.

Stark, citing studies by government agencies, said he presumed that part of the problem is that some doctors were "performing more and more services even when not necessary . . . bypasses when not necessary, cataract {surgery} way before necessary" to boost income by boosting volume.

He added that the average doctor "is doing pretty well" overall, saying doctors last year averaged $112,900 in net income before taxes.

Dr. James S. Todd, speaking for the American Medical Association, conceded there are some unnecessary patient services, but strongly disagreed that achieving higher income is the main reason for increased volume of services per patient.

"Most of this increase is attributable directly to Medicare beneficiaries receiving necessary and valuable services for their well-being," to shorter hospital stays requiring more intensive out-of-hospital doctor services, and to the rise in America's aged population, he said.

Roper, however, linked the main cause of the increase in Medicare physician payments to increased services -- "more ambulatory visits and labor and radiology tests" as well as "upcoded services," the classifying of certain procedures in higher-repayment categories than justified.

Roper said that while some treatment clearly improved health and helped patients, some studies have shown that some increases in volume of services per patient "exist without producing clinically meaningful differences in health outcome." For example, one major study found that 14 percent of heart bypasses were "clearly inappropriate" and 30 percent were of questionable value, Roper said.

Unlike Stark, he did not assign any motive to such "overutilization," but said that if Medicare costs are to be held down, a number of options are open. These include refusing to pay for services later found inappropriate, giving physicians a single fixed payment for a cluster of related services to a patient instead of letting them bill separately for each, limiting fees for services that appear overpriced, and encouraging greater use of prepaid plans.