The most dramatic proposal in President Bush's $525 billion budget for the Health and Human Services Department would introduce an element of means-testing into Medicare by tripling the premium for high-income people on the doctor-insurance portion of the program.

Instead of $31.80 a month next year, those with at least $125,000 income would pay $95. Proponents of changing Medicare's "Part B" program say it is heavily subsidized by the Treasury and the rich don't need a subsidy.

The budget proposal involving the most money, however, is a plan to cut $25 billion over the next five years from anticipated Medicare payments to hospitals and doctors. The proposal has been condemned by spokesmen for those groups and some members of Congress.

Under Medicare, no premium is charged for hospital benefits, known as Part A, which are financed through the Social Security payroll tax. As a result, said Merton Bernstein of Washington University law school, "a $50,000 earner pays a five-times higher Medicare payroll tax than a $10,000 earner." Under Medicare, a person can opt out of Part B coverage without losing Part A.

The Part B premium is $29.90 a month but will rise to $31.80 next year. It covers 25 percent of the cost of the program, and the Treasury pays the other 75 percent from general tax revenues. The 1992 Part B subsidy provided by the Treasury will come to about $40 billion.

The administration wants Congress to cut that subsidy by tripling the Part B premium for people with adjusted gross income over $125,000 ($150,000 for a couple). This would raise their premium to 75 percent of the cost, or $95 a month -- about $1,140 a year. Those below the cutoff would continue to pay $31.80.

About 600,000 people would be affected the first year, officials said yesterday. The proposal would save the Treasury $1.2 billion over five years. Next fall, Medicare would send inquiry forms to enrollees that had high incomes in the past to ask if they expected 1992 incomes above the cutoff. The extra premiums would then be deducted from their Social Security checks. If they had no such checks, they would be billed.

The proposal, strictly speaking, is not a full means-test. It bases the size of the premium on income, but does not exclude people from the program on the basis of income, which has never been done. Rep. Edward R. Roybal (D-Calif.), however, has indicated he feared the Bush plan could be a foot in the door for a flat means-test.

Senate Finance Committee Chairman Lloyd Bentsen (D-Tex.) said the Bush proposal "has some merit, but the administration has a history of flirting with this one, then dropping it like a hot potato. . . . Instead of dealing with {national} health care costs of over $600 billion a year and rising, they're trying to distract us with talk about means-testing, a $1.2 billion budget item."

The American Association of Retired Persons dismissed the proposal as a "warmed over" retread from the past. Rep. Fortney "Pete" Stark (D-Calif.), chairman of the House Ways and Means subcommittee on Medicare, said, "The wealthy should pay more for all government, not just Medicare," and several Democrats said privately they saw it primarily as a Bush administration effort to counter the Democrats' use of the "fairness" issue on taxes.

Although officials said that few high-income Medicare beneficiaries would drop out of Part B -- because they still would be getting a 25 percent subsidy -- former Social Security commissioner Robert Ball said the proposal "presents a lot of problems." He fears dropouts, especially among those 65 to 70 who are least likely to get sick, which would reduce savings. In addition, he said, many people might oppose the plan for fear the $125,000 cutoff would be pushed lower and lower over time.

However, Sen. John H. Chafee (R-R.I.) said, "This proposal deserves serious consideration in the context of taking care of the uninsured . . . in the context of larger health-care reform, not for deficit-reduction."

Rep. Willis D. Gradison Jr. (R-Ohio), senior Republican on the House Budget Committee and the Stark subcommittee, has long backed the concept of relating premiums to income, an aide said, though he is not endorsing the specifics of the current plan. An income-related premium was a key feature of the Medicare catastrophic-benefits law that Stark and Gradison sponsored but was so detested by seniors that Congress repealed it.