Britain’s biggest energy company, Centrica, is facing calls for a boycott after it emerged a US subsidiary gave thousands of pounds to a think tank that promotes climate science denial – even though the company claims to be a “world leader” on action to address global warming.

A list of donors to the Texas Public Policy Foundation (TPPF), which was leaked to the Texas Observer, shows Direct Energy gave US$20,000 in 2010.

And Centrica, which owns British Gas, told environmental campaign group Greenpeace that it had continued to provide funding since then, although it did not provide further figures.

As the biggest electricity and gas supplier in the UK, serving about 11 million homes, Centrica’s business involves producing a large share of the country’s greenhouse gases.

However the company says it is internationally recognised as “a global leader for action and disclosure on climate change” and insists it believes “climate change is one of society’s greatest global challenges”.

This view contrasts sharply with those of the TPPF, which has been praised by climate science denier Rick Perry – who will be US Energy Secretary under President Donald Trump – for opposing the “hysteria of global warming”.

At the TPPF’s third annual energy and climate policy summit earlier this month, Senator Jim Inhofe, who once took a snowball into the Senate as evidence against global warming, was one of two keynote speakers.

It appeared from Mr Inhofe’s speech that the event was designed for climate science deniers.

He told the audience that “all of my heroes” were in attendance and added: “I look at each one of you as an army of 200, you are voices out there in the wilderness with me and I love all of you for it.”

Mr Inhofe said he had initially believed scientists’ warnings about climate change.

“I assumed that was probably right until I found out about the cost,” he said.

“I started looking at it and started talking to some of the scientists… and that’s when I used the nasty word ‘hoax.’”

Unlike Mr Trump, who has said China was behind the ‘hoax’, Mr Inhofe claimed it was a plot by the UN dating back to the 1970s to create a global carbon tax as a source of funds not reliant on member states.

“If they are able to come up with a carbon dioxide tax or something like that, they don’t have to be accountable to anyone,” Mr Inhofe said. “That’s really what it’s all about.”

In June this year, 31 scientific bodies wrote to the US Congress with the basic message that climate change is real, is already happening and is being caused by greenhouse gases produced by human activities.

After a near 1C increase in temperatures in little over a century some species are already struggling to cope, with evidence of significant local extinctions of plants and animals.

The Arctic is set to be almost completely free of sea ice for the first time in nearly 100,000 years, opening up new shipping lanes and, ironically, allowing oil exploration in previously inaccessible areas.

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A number of small islands in the South Pacific have also disappeared.

TPPF has also received money from oil firms such as ExxonMobil, Chevron and the Koch brothers, business tycoons who have provided large amounts of money to fund opposition to measures designed to address climate change.

Craig Bennett, chief executive of environmental campaigners Friends of the Earth, suggested people might want to avoid buying gas and electricity from Centrica because of its support for the group.

“Until companies think twice about where they put their money, and what that money supports, consumers may think twice about where to buy their energy in the first place,” he said.

Green Party MP Caroline Lucas said: “For a company that has claimed to be at the forefront of action on climate change, it is simply astounding that Centrica is donating money to climate deniers.

“Now that these links have come to light, we need a clear commitment from Centrica to end all further donations. It is shameful that one of our largest energy companies is linked to this reckless and irresponsible organisation, and I hope an apology will be issued shortly.”

And she added: “If you’ve ever thought of switching supplier, now is the time to do it!”

Dale Vince, founder of UK renewable energy company Ecotricity, called for a boycott.

“The biggest single cause of climate change in our country is energy… and so British Gas being the biggest single supplier of gas and electricity in the land are simultaneously the biggest cause of climate change,” he said.

“And they are actually funding climate change denial? Well, I think that’s incredible.”

Centrica told The Independent that the money given to TPPF was not related to its stance on climate change, but because it looked into tax policies, healthcare, “safe neighbourhoods” and other issues of concern to the subsidiary’s staff in the US.

However a spokesman for the firm said the money it gives goes into a central fund and is not ring-fenced for any particular project.

In an emailed statement, Centrica said: “We have a very clear position on climate change and we believe in the need to take material action to reduce the effect of fossil fuels on climate change.

“We believe the science around climate change is clear and there is an urgent need for precautionary action including setting a meaningful price for carbon dioxide and shifting the energy mix towards a lower carbon future.

“Centrica has been identified as a global leader for action and disclosure on climate change by CDP, an international non-governmental organisation reporting to investors representing around a third of the world’s invested capital.”