Media playback is unsupported on your device Media caption Lawyer David B Rivkin Jr tells Radio 4's Today Scott Pruitt 'absolutely cares about the environment'

US President-elect Donald Trump has chosen an outspoken critic of President Obama's climate change policies to head the Environmental Protection Agency.

Oklahoma Attorney General Scott Pruitt, 48, is seen as an ally of the fossil fuel industry.

He has been a key player in legal challenges against EPA regulations on greenhouse gas emissions.

Democrats and environmentalists in the US have expressed dismay, calling Mr Pruitt a climate change denier.

News of Mr Pruitt's appointment emerged on Wednesday evening. Mr Trump formally confirmed it in a statement on Thursday.

"For too long, the Environmental Protection Agency has spent taxpayer dollars on an out-of-control anti-energy agenda that has destroyed millions of jobs," Mr Trump was quoted as saying.

Mr Pruitt would "reverse this trend and restore the EPA's essential mission of keeping our air and our water clean and safe", he said.

What Scott Pruitt believes

Mr Pruitt has sued the EPA on several occasions, most recently over Mr Obama's Clean Power Plan, which aims to reduce carbon emissions from power plants.

He called the move "an unlawful attempt to expand federal bureaucrats' authority over states' energy economies in order to shutter coal-fired power plants".

And, writing in the National Review in May, Mr Pruitt said of climate change: "That debate is far from settled.

"Scientists continue to disagree about the degree and extent of global warming and its connection to the actions of mankind."

Image copyright AP Image caption Mr Pruitt has challenged Barack Obama's plan to reduce power plant emissions

There is consensus among the majority of scientists in the field that carbon emissions from human activities are a key driver of rising temperatures and that the impact of climate change will be severe.

In the statement confirming his appointment, Mr Pruitt said Americans were "tired of seeing billions of dollars drained from our economy due to unnecessary EPA regulations".

He said he would run the EPA in a way that fostered "both responsible protection of the environment and freedom for American businesses".

Clear signals: Matt McGrath, environment correspondent

The nomination of Scott Pruitt has two important ramifications. The first is a clear signal from the incoming Trump administration that environmental regulations, especially as they apply to the production of energy, are set for fundamental reform.

The second implication is that the Trump camp is not willing to accept that many aspects of the science of climate change are now settled.

In his official biography, Mr Pruitt revels in his role as a "leading advocate against the EPA's activist agenda".

Mr Pruitt has engaged in legal fights with the federal government on a number of issues, including Obamacare, but it is in fighting the EPA and President Obama's climate regulations that he has really shone.

As the chief law officer of a major energy-producing state, Mr Pruitt has taken a lead role in the 28-state challenge to the Clean Power Plan.

He has also secured an injunction blocking the EPA's "Waters of the US" rule, which expands the scope of the Clean Water Act.

Read more from Matt: Trump nominee to rekindle climate battle?

Where does Trump stand?

Mr Trump, in a speech on energy on the campaign trail in May, castigated the Obama administration's environmental initiatives. He promised to scrap "any regulation that is outdated, unnecessary, bad for workers, or contrary to the national interest".

He also pledged to "cancel" the Paris climate deal, which came into force in November.

The landmark agreement commits governments to moving their economies away from fossil fuels and reducing carbon emissions to try to contain global temperature rise.

But last month, in an apparent softening, he acknowledged in a meeting with the New York Times that there was "some connectivity" between human activity and climate change.

And as news of Mr Pruitt's appointment was emerging on Wednesday, Mr Trump met actor and climate change activist Leonardo DiCaprio.

Terry Tamminen, CEO of the Leonardo DiCaprio Foundation, said they presented Mr Trump with a plan on job creation through "clean, renewable energy generation".

What his critics say

The news of Mr Pruitt's selection for EPA head comes as a blow to Democrats and environmentalists.

Image copyright Twitter

"Attorney General Pruitt's reluctance to accept the facts or science on climate change couldn't make him any more out of touch with the American people, and with reality,'' said Chuck Schumer, the incoming leader of the Senate Democrats.

"President-elect Trump promised to break the special interests' grip on Washington, but his nomination of Mr Pruitt - who has a troubling history of advocating on behalf of big oil at the expense of public health - only tightens it."

Democrat Senator Bernie Sanders called the move "sad and dangerous".

Meanwhile, Fred Krupp, of the Environmental Defense Fund, called Mr Pruitt "a deeply troubling choice to head the agency that protects the clean air all Americans breathe and the clean water we drink".

But Jim Inhofe, a Republican senator from Oklahoma who called global warming a "hoax", said Mr Pruitt had "fought back against unconstitutional and overzealous environmental regulations... he has proven that being a good steward of the environment does not mean burdening taxpayers and businesses with red tape".