Human beings are flushing millions of tonnes of solid waste into rivers and oceans every day, poisoning marine life and spreading diseases that kill millions of children annually, according to the UN.

"The sheer scale of dirty water means more people now die from contaminated and polluted water than from all forms of violence including wars," the United Nations Environment Programme said.

In a report entitled Sick Water for World Water Day, UNEP said the two million tonnes of waste, which contaminates over two billion tonnes of water daily, had left huge "dead zones" that choke coral reefs and fish.

It consists mostly of sewage, industrial pollution, pesticides from agriculture and animal waste.

The report said a lack of clean water was killing 1.8 million children under five every year. Much of the waste came from developing countries, which dump 90 per cent of their wastewater untreated.

Diarrhoea, mostly from dirty water, kills around 2.2 million people a year, it said, and "over half the world's hospital beds are occupied with people suffering from illnesses linked with contaminated water."

The report recommends water recycling systems and multi-million or multi-billion dollar water sewage treatment works."

It also suggests protecting wetlands, which act as natural waste processors, and saving animal waste to use as fertiliser.

"If the world is to... survive on a planet of six billion people heading to over nine billion by 2050, we need to get smarter about how we manage wastewaters," said UNEP director Achim Steiner. "Wastewater is quite literally killing people."