GENEVA- One billion people worldwide still practice "open defecation" and they need to be told that this leads to the spread of fatal diseases, U.N. experts said today at the launch of a study on drinking water and sanitation.

Societies that practice open defecation, putting them at risk from cholera, diarrhoea, dysentry, hepatitis A and typhoid, tend to have large income disparities and the world's highest numbers of deaths of children under 5 years old.

Although the prevalence of open defecation is in decline, it is often common in fast-growing populations, so the total number of people doing it is not falling so fast, or is even rising.

The country with the largest number of public defecators is India , which has 600 million. India 's relatively "hands off" approach has long been at odds with the more successful strategy of neighboring Bangladesh, which has put a big focus on fighting water-borne diseases since the 1970s, said Luyendijk, a statistician at the U.N.'s children's fund UNICEF.

"The Indian government did provide tremendous amounts, billions of dollars, for sanitation for the poorest," he said.

"But this was disbursed from the central level to the provinces and then all the provinces had their own mechanisms of implementing. And as their own data showed, those billions of dollars did not reach the poorest," added Luyendijk.

"What is shocking in India is this picture of someone practicing open defecation and in the other hand having a mobile phone," said Maria Neira, director of Public Health at the WHO.