China's three biggest power firms produced more greenhouse gas emissions last year than the whole of Britain, according to a Greenpeace report published today/yesterday.

The group warned that inefficient plants and the country's heavy reliance on coal are hindering efforts to tackle climate change. While China's emissions per capita remain far below those of developed countries, the country as a whole has surpassed the United States to become the world's largest emitter.

Greenpeace said the top 10 companies, which provided almost 60% of China's total electricity last year, burned 20% of China's coal — 590m tonnes — and emitted the equivalent of 1.44 billion tonnes of carbon dioxide.

The efficiency of Chinese power generation compares unfavourably with other countries. In Japan, 418 grams of carbon dioxide are emitted per kilowatt hour and in the US, the equivalent figure is 625 grams. But most of the top 10 firms in China produce 752 grams of CO2.

"China is suffering the pains of extreme weather events such as droughts, heat waves, typhoons and floods, worsened by climate change. These power companies can and must help China to prevent climate disaster by rapidly increasing efficiency and the share of renewable energy such as wind and solar," said Yang Ailun, Greenpeace's climate campaign manager, at the launch in Beijing of the Greenpeace report, Polluting Power: Ranking China's Biggest Power Companies.

The report says that in 2008, Huaneng, Datang and Guodian — the top three firms — emitted more greenhouse gases than the whole of the United Kingdom.

But Yang added: "China is ideally placed to…[become] the world's superpower in terms of smart energy and renewable energy."

The group said China closed down 54.07 gigawatt of the least efficient coal-fired plants over the last three and a half years — more than the total electricity installed capacity of Australia.

It urged power firms to phase out all inefficient coal-fired plants under 100 megawatt by 2012, saving 90m tonnes of coal consumption and 220m tonnes of carbon dioxide annually.

Firms are already turning to renewable energy and by the end of last year Guodian had installed 2.88 gigawatt of wind power; almost 24% of China's total and enough to make it the biggest wind energy firm in Asia.

But Greenpeace said only three of the top 10 produced 10% or more of their energy from renewable sources. The vast majority relied heavily on hydropower — with eight of the firms not even halfway to their legal obligation to produce 3% of energy from other renewable sources by 2010.

Greenpeace urged the Chinese government to impose energy and environment taxes on coal, encouraging increased efficiency and a move to renewable sources.

It also called for a doubling of the national renewable energy target to 30% by 2020 and for stricter efficiency standards for coal-fired power stations.

The State Council, China's cabinet, is currently drawing up plans for a massive "new energy" programme to cut emissions and ensure energy security. Reports in the domestic media and from foreign diplomats suggest the next decade could see between 1.4 trillion (US$200 bn) and 4.5 trillion yuan (US$600bn) investment in projects ranging from nuclear power, low carbon transport and clean coal technology to super-efficient electric grids.

This huge expansion is already causing problems. Manufacturing capacity is outstripping supply and the country's under-invested power grid networks were not ready for large-scale wind power input. Some wind farms have been unable to start operating because of a lack of grid connection or were operating at levels lower than planned.

But experts warn that de-carbonising the energy supply must happen fast, given the massive toll on China's environment. State news agency Xinhua reported yesterday that the country's largest desert lake could vanish in decades due to climate change and human activities.

"Just 10 years ago, one couldn't see the other bank of the Hongjiannao even through a telescope. Today, it's visible with the naked eye," said He Fenqi, a researcher with the Chinese Academy of Sciences.

The Hongjiannao, sandwiched between the Muus Desert in Shaanxi Province and the Erdos Plateau in Inner Mongolia, has shrunk by at least 30% in the past two decades, Xinhua reported. It now covers 4,600 hectares and its water level is declining by 20 centimetres annually.