Greenpeace campaigners seeking the axing of plans for a new coal-fired power station in Kent have presented a petition to Medway Council.
The new units may be equipped to store carbon dioxide underground
Proposals have been put forward by E.ON UK to build Britain's first new coal plant for 20 years at Kingsnorth.
Thousands of postcards signed by the public were given to the council.
Greenpeace fears a widespread return to coal use and more carbon emissions, but E.ON said efficiency improvements would make it more environmentally friendly.
Robin Oakley, of Greenpeace, said more than 10,000 people opposed the scheme.
"We know that there's also been over 3,000 e-mails concerning this issue to the council too," he said.
"Many thousands of the people concerned are actually based in Kent themselves - they're local people."
E.ON UK submitted its planning application to build two new cleaner coal units at Kingsnorth power station, near Rochester, last December.
The company said the units would use "state-of-the-art technology" to ensure a reduction in carbon emissions of around two million tonnes a year.
That would be "equivalent to taking half a million cars off the UK's roads", it said.
'Carbon belching dinosaur'
E.ON has also suggested excess heat from the plant could supply 100,000 homes and associated commercial and public service buildings, eliminating the need for gas boilers.
But Mr Oakley has maintained that coal is still "one of the most polluting fuels of all", emitting more climate-changing CO2 than any other kind.
"Obviously we know the impacts of this - global warming - we've seen flooding this year, and in the past we've seen heat waves, and I think people are concerned that in this day and age someone's proposing to build one of the dirtiest kinds of power station that we know.
"The proposal uses a technology that's little better than the power stations being built 30 years ago."
A decision on the future of the site has yet to be taken by Medway Council.
Mr Oakley added: "This is one of the most important decisions that Medway Council could ever make.
"Obviously, we hope they'll make the right decision for Kent and for the planet, and ditch plans for this carbon belching dinosaur."