WASHINGTON—Cutting the U.S. corporate tax rate to 20% from 35% would, “very conservatively,” boost average household income by $4,000 a year, White House economists said in a report released Monday.

The study, which comes as the tax-policy debate heats up in Congress, stakes its argument on the idea that corporate taxes hurt workers by inhibiting capital investment, hiring and wage growth.

“There’s lots of evidence that wages respond to changes in corporate taxes,” Kevin Hassett, chairman of the White House Council of Economic Advisers, told reporters Sunday.

Many economists, however, say a corporate-tax cut would mostly benefit shareholders, not workers.

The $4,000 wage increase would occur over a few years as companies invest more in the U.S., boosting productivity and then wages, Mr. Hassett said. That would be on top of average household income—or the total income divided by the number of households—of about $83,000. The pay gain for the $53,000-a-year median household, which is the level at which half of households earn more and half earn less, would be closer to $3,000.