WASHINGTON — An election-year plan by House Republicans to simplify the tax code would cut income tax rates but impose a new surtax on some high-income families.

The plan, which is to be unveiled Wednesday, would lower the top income tax rate from 39.6 percent to 25 percent, said a GOP aide who spoke on condition of anonymity. However, the plan would impose a new 10 percent surtax on some earned income above about $450,000.

Republicans have touted the upcoming plan as a major overhaul of the tax code that would dramatically lower tax rates for individuals and corporations, but recoup the revenue by eliminating or reducing popular tax breaks. Overall, the plan is designed to raise about the same amount of tax revenue as the current system, though the system would be much simpler.

It is an important political point for Republicans that the plan is not seen as a big giveaway to the rich. The new surtax on high-paid workers would help ensure that wealthy taxpayers as a group continue to pay about the same amount as they pay today, said the GOP aide.

The issue of whether to increase overall tax revenue is a major sticking point among Republicans and Democrats. Most Republicans in Congress adamantly oppose anything that looks like a tax increase, while Democratic leaders insist that any attempt to overhaul the tax code raise additional revenue. President Barack Obama and Senate Majority Leader Harry Reid, D-Nev., have said they want to target tax breaks for corporations and the wealthy.

Obama has said he supports corporate tax reform, but he has shown little interest in overhauling the tax code for individuals.

Rep. Dave Camp, R-Mich., has been working to overhaul the entire tax code for about three years, since he became chairman of the tax-writing House Ways and Means Committee.

Camp is expected to say Wednesday which tax breaks he would eliminate to pay for lower overall rates.