The Republican-led US Congress began its first session in turmoil on Tuesday as the House of Representatives backed away from a decision to defang an ethics watchdog after a public outcry, including a dressing-down from the president-elect.

With Donald Trump, set to be sworn in as president on January 20, Republicans will control both the White House and Congress for the first time since 2007, and they were set to begin laying plans for enacting his agenda of cutting taxes, repealing Obamacare and rolling back financial and environmental regulations.

But the moment was overshadowed by a surprise move by Republicans in the House of Representatives in a closed-door meeting late on Monday to weaken the independent Office of Congressional Ethics, which is in charge of investigating ethics accusations against legislators.

Trump, who campaigned on a pledge to "drain the swamp" and bring ethics reforms to Washington, was not pleased.

"With all that Congress has to work on, do they really have to make the weakening of the Independent Ethics Watchdog, as unfair as it may be, their number one act and priority," he said on Twitter on Tuesday.

"Focus on tax reform, healthcare and so many other things of far greater importance!"

Change of course

The ethics office was created in 2008, following several corruption scandals, but some legislators have charged in recent years that it has been too quick to investigate complaints from outside partisan groups.

With all that Congress has to work on, do they really have to make the weakening of the Independent Ethics Watchdog, as unfair as it — Donald J. Trump (@realDonaldTrump) January 3, 2017

Legislators wanted to have greater control of the watchdog, and inserted changes into a broader rules package, set to pass when the House convened on Tuesday.

Even before Trump's tweet, many House Republicans, including top leaders, opposed the measure and worried about its ramifications.

Trump's tweet prompted an emergency meeting and a quick change of course by Republicans.

"It was taken out by unanimous consent ... and the House Ethics Committee will now examine those issues," said AshLee Strong, a spokeswoman for House Speaker Paul Ryan, who was re-elected as speaker on Tuesday.

Since his election on November 8, Trump has made clear he wants to move swiftly to enact proposals he outlined during the campaign such as simplifying the tax code, slashing corporate tax rates and repealing and replacing President Barack Obama's signature health insurance programme, known as Obamacare.

'Lousy healthcare'

Republicans have long sought to dismantle Obamacare, insisting it was unworkable and hampered job growth. But they face a dilemma over how to provide health insurance for the 13.8 million people enrolled in Obamacare who could lose their coverage.

The law aims to provide health insurance to economically disadvantaged people and expand coverage for others.

Trump kept up his attack on Tuesday, tweeting: "People must remember that Obamacare just doesn't work, and it is not affordable," and adding, "It is lousy healthcare."