The world's 20 biggest commercial banks are responsible for 75% of emissions from the coal sector, according to a joint study released on the sidelines of the COP-17 climate change negotiations in Durban.

Coal-fired power plants are the biggest source of man-made carbon-dioxide emissions, said Heffa Schuking of Urgewald, the German ecological group that helped produce the study, titled "Bankrolling Climate Change" and released on Tuesday.

Urgewald worked with South African nonprofit group Earthlife Africa and the international NGO BankTrack to write the report.

The report focuses on 93 large international banks for their contributions towards coal finance since 2005 - the year the Kyoto Protocol came into force - including both mining and power stations.

The top "climate killers", as the report dubs them, are JPMorgan Chase, Citi, Bank of America, Morgan Stanley, Barclays, Deutsche Bank, Royal Bank of Scotland, BNP Paribas, Credit Suisse, UBS, Goldman Sachs, Bank of China, Industrial and Commercial Bank of China, Crédit Agricole/Calyon, UniCredit/HVB, China Construction Bank, Mitsubishi UFJ Financial Group, Société Générale, Wells Fargo and HSBC.

Coal financing rose from ?15bn in 2005 to ?33bn in 2010, according to the report. But Ms Schuking said that, as the report had surveyed only 93 large banks, the real figure could be double this amount.

Banks' financing of the coal sector is in sharp contrast to their everyday rhetoric, the report notes, as almost all have committed themselves to combating climate change.

Ending emissions from coal is a large part of the solution. Since coal-fired power plants cost more than $2bn to build, the logical question was to look at who is providing the money, Ms Schuking said, adding that public policy responses had been woefully inconsistent.

"If all coal-fired power plants scheduled to be built in the next 25 years come into operation, their lifetime carbon-dioxide emissions would be equal to those of all coal-burning activities since the beginning of industrialisation," she said, quoting from the World Development Report 2010.

"Climate change is already a fact of life, felt by vulnerable communities throughout the globe," she added.

All the data have been made public at Banktrack.org. Ms Schuking urged NGOs and civil society organisations to investigate whether their bankers were on the list.

"By naming and shaming these banks, we hope to set the stage for a race to the top, where banks compete with each other to clean up their portfolios and stop financing instruments that are pushing our climate over the brink. We want banks to act and we want them to act now," the authors said in the report.

Bobby Peek, director at South African clean air campaigner groundWork, said local banks were also complicit in funding climate change. He singled out Standard Bank and Nedbank for criticism, for lending ?99m and ?86m, respectively, to national power utility Eskom.

"Nedbank is often said to be carbon neutral, but its portfolio is far from carbon neutral," he said.

Mr Peek said banks had been hit by a drop in merger and acquisition activity and were looking to make up these earnings through investments in the power and infrastructure sectors.

He said coal had an environmental and social impact beyond its emissions. Local communities already suffered as a result of toxic mine dust, and in Mpumalanga, where 10 coal-fired power stations are located, air pollution standards were exceeded on more than 500 occasions between May and August last year. The impact of coal on human health was estimated at R4bn a year by the Department of Water and Environmental Affairs, he said.