Republican legislators are celebrating ahead of a major vote on the most sweeping overhaul of the nation’s tax laws in more than three decades.

House speaker Paul Ryan dismissed criticism of the widely unpopular package and insisted “results are what’s going to make this popular”.

Their long-sought political goal within grasp, Republicans are set to catapult the 1.5 trillion dollar (£1.2 trillion) tax legislation through the House, rolling over a dozen party defectors from high-tax states.

Senate majority leader Mitch McConnell said the Senate would vote on Tuesday evening, sending the legislation to President Donald Trump.

“When we get this done, when people see their withholding improving, when they see jobs occurring, when they see bigger paychecks, a fairer tax system, a simpler tax code, that’s what’s going to produce the results,” said Mr Ryan.

The bill provides steep tax cuts to businesses and wealthy families, and more modest cuts to middle and low-income families.

It scales back a popular deduction for state and local taxes, repeals a key tenet of Barack Obama’s Affordable Care Act and allows drilling in the Arctic National Wildlife Refuge.

Republicans acknowledged they still have to convince many Americans of the benefits of the bill, which polls poorly.

Many voters in surveys see the legislation as a boost to the wealthy, such as Mr Trump and his family, and only a minor gain for the middle class.

Senate majority leader Mitch McConnell
Senate majority leader Mitch McConnell said the Senate would vote on Tuesday evening, sending the legislation to President Donald Trump (J. Scott Applewhite/AP)

The complex legislation blends elements of separate House and Senate bills that were recently passed.

It permanently slashes the tax rate for corporations from 35% to 21%. The tax cuts for individuals are temporary, expiring in 2026.

It doubles the standard deduction used by about two-thirds of US households, to 24,000 dollars (£20,000) for married couples, also ending in eight years.

The 1,000 dollars (£846) per-child tax credit doubles to 2,000 dollars (£1,692), with up to 1,400 dollars (£1,184) available in refunds for families who owe little or no taxes.

Parents would have to provide children’s social security numbers to receive the child credit, a measure intended to deny the credit to people who are in the US illegally.

The legislation also repeals an important part of the health care law — the requirement that all Americans carry health insurance or face a penalty — as the Republicans look to unravel a law it failed to repeal and replace in the summer.

The package represents the first major legislative achievement for the Republicans after nearly a full year in control of Congress and the White House.