WASHINGTON - Critics say a proposal by Senate Finance Committee chairman Max Baucus to raise money for the health care overhaul by taxing insurers on their most expensive plans could hit middle-class pocketbooks - particularly in New England, where health costs are high.

Baucus has proposed paying for more than a quarter of his $750 billion health care proposal with a 35 percent excise tax on “gold-plated’’ insurance plans. It would be levied on insurance companies, which could pass on the expense to their customers.

The tax was meant to be a compromise, but it has already caused an uproar on both sides of the political aisle, with liberals and conservatives alike complaining it would hurt low- and moderate-income workers and older workers - particularly in high-cost areas.

The tax would hit about 10 percent of plans and 8 percent of taxpayers nationwide, according to Baucus’s aides, who said state-specific estimates were not available. It is designed to not only raise revenue but also to discourage employers from offering so-called Cadillac health insurance policies, generous plans that many economists say encourage people to use more health services than they need, driving up prices for everyone.

But critics say the tax would disproportionately affect workers who are sick - and therefore choose plans that have better benefits - or older, since older workers can be charged more for their insurance.

“A more expensive plan isn’t necessarily a better plan; it just may mean the workforce is older,’’ said Celia Wcislo, assistant division director of Service Employees International Union 1199 and a member of the Massachusetts Health Insurance Connector Authority board. She said people with plans that offer maximum flexibility may have an illness that requires them to see their doctor often or to consult a range of specialists.

The tax would apply only to the marginal difference between the cost of the plan and the price thresholds set in the bill - $8,000 for an individual plan and $21,000 for a family plan - not to the total cost of the policy. Baucus has included a three-year transition period to cushion the blow in the 17 most expensive states, including Massachusetts, which has the highest premiums in the country for family plans. But because the thresholds would rise each year at the rate of inflation - not medical inflation, which is much higher - the tax would probably affect a significant number of New Englanders within a few years.