Overhauling the tax code is a top priority for the Trump administration and congressional Republicans before next year's midterm elections. They insist that the broad tax cuts for corporations, small businesses and individuals will boost US economic and job growth.

But Democrats have criticized that the Republican tax legislation would mostly benefit the wealthy and large corporations and increase US budget deficit.

While the bill would reduce taxes on average for all income groups, the top one percent of households would receive the largest benefits, according to a new study by the nonpartisan Tax Policy Center published on Monday.

The study also found that the top one percent taxpayers would receive an average tax cut of 0.9 percent of after-tax income in 2027, while low- and middle-income taxpayers would see little change.

Economists have argued that the massive tax cuts to the wealthy would do little to boost economic growth but further widen US income inequality.

"US policymakers should be particularly concerned about the effects of any new tax legislation on the incomes of individuals and businesses because of rising income inequality in the United States and the relatively limited US social safety net financed with government taxes," Jacob Funk Kirkegaard, a senior fellow at the Peterson Institute for International Economics, wrote in a recent analysis.

While the Trump administration argued that the tax cuts would pay for themselves with faster economic growth, other analyses from independent think tanks and economists have found that the growth effects from tax cuts would be relatively small and US budget deficit would inevitably increase.