Republicans in the US House of Representatives have backed a proposal to take ethics oversight away from an independent group and give the authority to the legislators themselves.

The ethics change, which prompted an outcry from Democrats and government watchdog groups, is part of a rules package that the full House will vote on on Tuesday.

The proposal by Republican Congressman Bob Goodlatte of Virginia to gut the independent Office of Congressional Ethics, which already does not punish lawmakers, was approved 119-74.

House speaker Paul Ryan opposed changing ethics rules, but legislators disregarded his leadership on the issue.

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Goodlatte maintains that altering the ethics review process "strengthens the mission" of the office.

"It also improves upon due process rights for individuals under investigation, as well as witnesses called to testify. The [ethics office] has a serious and important role in the House, and this amendment does nothing to impede their work," he said in a written statement on Monday.

'First casualty of new Congress'

Democrat Nancy Pelosi of California, the House minority leader, voiced dismay.

"Republicans claim they want to 'drain the swamp,' but the night before the new Congress gets sworn in, the House GOP has eliminated the only independent ethics oversight of their actions.

"Evidently, ethics are the first casualty of the new Republican Congress," she said in a statement. "The amendment Republicans approved tonight would functionally destroy this office."

President-elect Donald Trump has used the expression "drain the swamp" in a pledge to fight corruption in Washington.

He will have a Republican-led House and Senate, when he is sworn in January 20.

"Trump's cabinet of billionaires & CEOs have ignored gov ethics rules & dragged their feet on FBI background checks & financial disclosure," Democratic senator, Elizabeth Warren, said on Twitter.