The head of China's environmental agency has blamed the rising number of riots, demonstrations and petitions across the country on public anger at pollution.

Echoing the language of the Cultural Revolution, Zhou Shengxian called for a "struggle" against polluters, and said the public refused to accept the increasing degradation of the environment.

His unusually outspoken comments underscore the frustration of state mandarins at local government officials who ignore environmental standards in order to attract investment, jobs and bribes.

Breakneck growth has turned China into a huge environmental disaster area. A soon-to-be-published World Bank report says some 500,000 people die each year as a result of pollution.

Beijing is trying to shift the economy on to a more sustainable development track. The state council - China's cabinet - tightened the water pollution law to require more testing, licensing and stiffer penalties, the state-run Xinhua news agency reported yesterday.

But factory owners who violate state guidelines are often protected by local officials. According to Mr Zhou, the state environmental protection administration chief, many plants build secret pipes to discharge polluting chemicals. Others release toxins when locals are asleep.

The China Daily quoted him as saying: "Some businesses don't rest deep in the night when they have no scruples about dumping pollution in rivers."

In a recent inspection of 529 firms along the Yellow, Yangtze and other major rivers and lakes, 44% had violated environmental laws, while almost half of the 75 waste water treatment facilities underperformed or did not work. Mr Zhou said some waterways resembled "sticky glue".

The absence of protection has stirred up discontent, he said, and prompted a growing number of "mass incidents", the term used to describe protests. He said petitions received by his agency this year were up 8%. While not endorsing protests, Mr Zhou called for local environmental officials to stand up to violators.

Demonstrations against power and chemical plants have become increasingly common in recent years. In May, thousands took to the streets of Xiamen, in Fujian province, leading to the suspension of a petrochemical plant. In 2005, police killed at least three villagers in Dongzhou, Guangdong province, while quelling a riot over a planned power plant.

Anger has been fuelled by unfair land grabs and health fears. According to the government, two-thirds of China's 595 cities now have unhealthy air.

Pollution scandals are common. Earlier yesterday, state media reported that tap water had been restored to 200,000 residents of Shuyang county in Jiangsu after a chemical spill halted supplies for 40 hours. The environment agency said more than a quarter of the seven main river systems were so polluted that the water was unfit for human contact.

The tendency towards secrecy has increased concerns. According to the FT, officials have tried to remove figures from a World Bank report that suggest up to 400,000 people in China die each year from outdoor air pollution, 30,000 from indoor air pollution, and 60,000 from water pollution. The government denies it has tried to interfere.