The British government will lose its leadership position on climate change and risk scuppering a global deal to cut emissions if it presses ahead with a new generation of dirty coal power, they say.
The US could now think twice before joining any post-Kyoto deal on climate change, the campaigners warn in their join letter to the UK foreign secretary David Miliband.
The heads of the Sierra Club, the Union of Concerned Scientists and the Natural Resources Defense Council say in their letter: "As proposed, these conventional coal plants lack any limits on their emissions of carbon dioxide and would drastically increase the UK's carbon dioxide emissions and make achievement of your stated pollution reduction goals extraordinarily difficult, if not impossible. Building new conventional plants and setting the UK up to fail and lose its leadership mantle will make our work in the US all the more difficult."
In the UK, there has already been heavy criticism of the plans to build new coal plants, without technology to capture and bury the large volumes of carbon dioxide emitted.
A recent report by the Institute for Public Policy Research (IPPR), a think-tank with strong ties to the ruling Labour party, said the European Union's goal of reducing emissions from the power sector and heavy industry through its emissions trading scheme would collapse if the new coal plants do come up in. And 75 more are in the pipeline across Europe.
The US intervention - signed by Carl Pope, the Sierra Club's executive director, Kevin Knobloch, the UCS president, and Frances G Beinecke, the NRDC director - follows an unprecedented campaign against new coal power in the US which has led to 66 of a proposed 150 new plants being abandoned or rejected by politicians and the courts, and most of the remainder locked in legal battles.
'If the UK takes a firm stand and rejects conventional coal it will send a strong, clear message to our new President and a new Congress, as well as to other countries considering new coal plants,' the letter adds.
Most immediate is the decision on whether to approve the first major planning application for a new coal plant at Kingsnorth in Kent, the site of this month's Climate Camp protest.
If Kingsnorth plant finally comes into being, several more could get the nod too. Without new technologies, these few big power stations would pump out so much carbon that Britain would miss essential targets. And where the first world falters, the third world can justifiably argue that it should not be asked to shoulder the burden.
Coal-burning in India and China would follow the UK's lead, with the world suffocating in the heat, Guardian newspaper warned.
Charting a way between the hard rocks of climate change and the jagged edges of energy security will depend on carbon capture, it says.
Carbon capture and storage (CCS) is an approach to mitigate global warming by capturing carbon dioxide (CO2) from large point sources such as fossil fuel power plants and storing it instead of releasing it into the atmosphere. But the technology is hugely expensive, and the British government is evasive on how far it would go to press manufacturers on that score.
At the very least, ministers must spell out clear duties on every new station to contribute to making the technology work. That cannot just mean installing a few removable pipes and setting aside space for a possible carbon tank some years down the line. Pending climate catastrophe demands a bolder response, Guardian said.