US Republicans have begun rolling back Obama-era gun regulations in the knowledge they have a gun-rights ally in the White House, striking down a rule aimed at keeping guns out of the hands of the mentally ill.

Welcomed by the gun lobby, the move sparked outrage among Democrats, who warned it could lead to more gun-related deaths.

The Republican-controlled Congress also moved to reject environmental laws put forward by Mr Obama, which comes as Mr Trump mulls an executive order to expand religious freedom.

Social-security recipients with a mental disorder looking to purchase a gun would no longer need to undergo extended background checks under the new proposal, which needs to be approved by the Republican-controlled Senate.

Passed last year, the law affects those on social security with a mental disorder such as severe anxiety or schizophrenia who need a representative to manage their benefits. It was opposed by the gun lobby and some disability advocates.

Mr President @POTUS – how can you want 'extreme vetting' to stop Islamic terrorists but extreme LACK of vetting on crazies buying guns?

— Piers Morgan (@piersmorgan) February 2, 2017

Democrats criticised the new attempt to roll back the stricter laws, arguing that doing so could lead to more gun-related deaths.

Accusing the Republicans of “weakening our firearms background check system”, they are mobilising to attempt the repeal in the Senate.

“Senate may vote today to weaken background checks on gun purchases. Call your Senator to oppose this change—ensure your voice is heard!” wrote Senator Dianne Feinstein of California.

But the move was welcomed by the influential gun lobby, the National Rifle Association (NRA), which has dubbed itself “Trump’s strongest ally”.

“The Obama administration’s last-minute, back-door gun grab would have stripped law-abiding Americans of their Second Amendment rights without due process,” said Chris Cox, executive director of the NRA’s Institute for Legislative Action.

“Today’s vote was the first step in revoking this unconstitutional action.”

Environmental laws

Barack Obama passed laws to increase gun background checks on the mentally ill. Photo: EPA

The Republican-led Senate also approved a regulation imposed late in Mr Obama’s term that prevented the dumping of coal mining debris into nearby waterways.

Republicans and some Democrats argue there are enough existing regulations in place and that the new law could risk coal-related jobs.

The majority of Democrats and other critics described it as a win for big polluters and an attack on clean water.

Republicans also plan to target rules around fracking among other regulations enacted late in Mr Obama’s term.

‘Religious freedom’

Meanwhile, a leaked copy of a Trump administration executive order aimed at expanding “religious freedom” has prompted concerns of an increase in legal discrimination.

LGBT and women’s groups are gearing up to oppose the measures, which they fear may allow employers to deny women contraception coverage, deny service to gay customers or dismiss workers based on their sexuality or gender identity.

The rules would greatly expand the definition of a religious organisation to encompass any organisation, including for-profit corporation, “operated for a religious purpose, even if its purpose is not exclusively religious.”

While not confirming the order would be signed, White House press secretary Sean Spicer often the government had imposed regulations that “denied people the ability to live according to their faith,” he said.

Similar laws were enacted by Vice-President Mike Pence while he was governor of Indiana.