It was hailed as one of the engineering feats of the 20th century. Now the Three Gorges Dam across China’s mighty Yangtze River threatens to become an environmental catastrophe.

In an unprecedented admission of blame, Communist Party officials gave a stark warning yesterday of impending disaster in the vast area around the dam if preventive measures are not urgently introduced.

For more than a decade China has promoted the world’s biggest hydro-electric project as the best way to end centuries of floods along the basin of the Yangtze and to provide energy to fuel the country’s economic boom.

The Government ignored critics who claimed that the Three Gorges, first proposed nearly a century ago and immortalised in a poem by Mao Zedong, was an ecological disaster waiting to happen.

Now those same officials who oversaw construction of the £13 billion dam admit that surrounding areas are paying a heavy, and potentially calamitous, environmental cost. Hundreds of thousands of people may have to be moved. A total of 1.3 million have been displaced by the dam already.

A report issued by the Xinhua news agency, mouthpiece for the Government, said: “There exist many ecological and environmental problems concerning the Three Gorges Dam. If no preventive measures are taken, the project could lead to catastrophe.”

A government forum listed a host of threats such as conflicts over land shortages, ecological deterioration as a result of irrational development and, especially, erosion and landslides on steep hills around the dam. Other authorities have already raised concerns over algae bloom downstream from the Three Gorges and a deterioration in aquatic life.

Wang Xiaofeng, director of the administrative office in charge of building the dam, said that it was time to face up to the environmental consequences of a project hailed as an achievement to rival the Great Wall.

He said: “We absolutely cannot relax our guard against ecological and environmental security problems sparked by the Three Gorges project. We cannot win passing economic prosperity at the cost of the environment.”

He revealed that the Prime Minister, Wen Jiabao, had discussed the problems surrounding the dam during a Cabinet meeting this year.

The timing of yesterday’s warning is significant, coming just two weeks before the Communist Party holds a five-yearly congress at which it will cement policy and anoint a new generation of leaders. One political analyst said: “It is a way for President Hu Jintao to distance himself [from the Three Gorges project] further. He stayed away from the completion ceremonies a year ago and this underlines that his administration does not want to be associated with the Three Gorges.” The project to create a dam producing more than 18,000MW of power – 20 times more than the Hoo-ver Dam in America – has been dogged by controversy. In 1989 one vice-premier ordered a five-year moratorium on any discussion about the dam, but that was ignored when conservatives gained power after the Tiananmen Square crackdown in the same year. In 1992 the virtually toothless National People’s Congress, or parliament, approved the dam – but with one third of deputies voting “no” or abstaining.

Dai Qing, an environmental activist, has been the most vocal opponent of the Three Gorges. She said: “We have never stopped talking about the problems but our voice was too weak. The system does not listen to the voices of civic activists or dissidents. But now, at last, they are starting to hear.”

One of the most worrying consequences of the project has been the sharp increase in landslides around the dam. Studies by geologists have shown that the water seeping out of the reservoir and the huge pressure changes are weakening the banks.

One official said that the shore of the reservoir had collapsed in 91 places and a total of 36 kilometres (22 miles) had already caved in.

Landslides have produced waves as high as 50 metres (165ft). In July a mountain along a tributary collapsed, dragging 13 farmers to their deaths and drowning 11 fishermen.

Ms Dai told The Times: “The Government knows it has made a mistake. Now they are afraid that the catastrophe that they cannot prevent will spark civil unrest. So they want to go public before the troubles start.”

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