Myron Ebell, the controversial advisor to Donald Trump who describes himself as an enemy of environmentalism, has visited No 10 Downing Street.

The climate change denier led Mr Trump’s transition team for the Environmental Protection Agency until the inauguration. Since then, Mr Ebell has returned to his job at an anti-environmentalist think tank.

It isn’t clear why Mr Ebell was attending Theresa May’s office, who he spoke to when he was there or what he spoke about. But it came a day after a briefing where Mr Ebell said that he was sure that Mr Trump would pull out of the Paris climate accord, and indicated that he and Mr Trump agreed that it was “pretty clear that the problem or the crisis has been overblown and overstated”.

He told that event that he doubted the science about climate change, which is agreed on by almost every scientist.

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Ebell has previously criticised those working for the UK Government to fight climate. In 2005 he said the then UK Chief Scientist David King was “an alarmist with ridiculous views who knows nothing about climate change”.

Mr King is now foreign secretary Boris Johnson's special representative for climate change.

During the briefing in London on Monday, Ebell made his anti-scientific stance clear. “There hasn't been much warming for the last 20 years, or statistically no warming for the last 20 years, but it is going to happen because we keep pumping more carbon dioxide into the atmosphere,” he said.

“Since 1996, that is the year before the Kyoto Protocol was negotiated, over 30 per cent of greenhouse gas emissions since the era of fossil fuels began in around 1750 have been emitted. Now, if we were going to have some warming, it should have started.

“The fact is that the sensitivity to carbon dioxide, the sensitivity to the climate, has been vastly exaggerated.

“In all of this discussion of the impacts of global warming, the benefits of higher carbon dioxide levels and of warming...are completely minimised by the alarmist community.”

Asked why Mr Ebell was there, a Downing Street spokeswoman said: “He was in for a meeting with advisers in his capacity as director of the think tank, the Competitive Enterprise Institute.

“This was part of regular engagement between Number 10 with various different think tanks and others. He was there in that capacity, it was a meeting between him and staff in Number 10, it wasn’t with the PM.”

It is understood climate change was not discussed at the meeting and that no ministers were present.

Caroline Lucas, co-leader of the Green Party, said she had tabled a parliamentary question to ask what Mr Ebell was doing at Number 10.

“Myron Ebell’s visit to Downing street is deeply alarming. He is a known climate change denier and his utterly misguided approach has no place in our politics.

“If Trump pulls out of the Paris agreement, and the Prime Minister did nothing to try and stop him, then she must accept some responsibility for such a hammer blow to the climate movement.

“Theresa May must tell us what Ebell was doing in Downing Street and confirm whether or not she brought up climate change with President Trump."

Greenpeace UK executive director John Sauven said: "Theresa May has some explaining to do. What was a former Trump adviser and notorious climate sceptic doing at No10? Has the prime minister agreed her staff can meet with the archenemy of the Paris climate agreement she has pledged to honour?