A water purification filter created by Australian scientists has pipes just 10,000th the width of a human hair and could provide relief to millions of people without access to safe drinking water.

The membrane, treated with plasma to boost the water absorption rate through nanotubes, removes contaminants and salt from dirty water, said Professor Kostya Ostrikov of the CSIRO.

The membrane can be fitted into portable purification devices the size of a teapot that would be rechargeable, inexpensive and more effective than many existing purifiers, he said.

"The plasma-treated carbon nanotubes are like security gates,'' he explained. ''The main flow, the water molecules, can get through, while suspicious contaminants are identified, isolated and prevented from entering."

More than 10 per cent of the world's population, or 783 million people, have no access to clean water, United Nations figures show. Cases of diarrhoea, which kills 801,000 children a year aged five and under, mostly in developing countries, can be drastically cut with improved water and sanitation.