China's rapid economic growth has left its rivers polluted and more than 300 million people without clean drinking water, a top lawmaker has said.
China needs to clean up its water supply
The figure showed the scale of the challenge facing China's leaders as they try to tackle pollution.
The lawmaker, Sheng Huaren, said laws to prevent pollution had failed.
Beijing has asked local authorities to improve water standards, but with no promise of funding it is unlikely any action will be taken.
A BBC correspondent in Beijing says more than 90% of urban China already suffers from some degree of water pollution.
But the situation is far worse in the countryside, where the drive for wealth has led to many unregulated factories dumping toxic pollutants into rivers and lakes.
The scale of the challenge was also highlighted by China's senior environmental official, Xie Zhenhua,
director of the State Environmental Protection Agency (SEPA).
He was quoted by the country's official Xinhua news agency as saying one of the key problems that the government currently needed to face up to and solve was that some local environment authorities do not exercise their law enforcement duties.
"Non-enforcement and lax enforcement of laws and administrative inactivity are the main targets we will aim at," he said.
This week's warnings follow similar alarms issued in March, when officials said that more than 70% of China's rivers and lakes were polluted.