Out of a total of 147 countries, it ranks Finland top followed by Canada, Iceland, Norway, Guyana, Suriname, Austria, Ireland, Sweden and Switzerland.

At the bottom end of the scale, Haiti lies at 147th, preceded by Niger, Ethiopia, Eritrea, Malawi, Djibouti, Chad Benin, Rwanda and Burundi.

Not surprisingly, almost all the most water-rich nations are in the northern hemisphere and almost all those with the least water are in Africa.

But, in a departure from usual practice, the researchers did not only use access to good quality water as their benchmark.

They took five different criteria to construct their index - resource, access, use, capacity and environment.

Research team leader Caroline Sullivan said this explained why rich nations like the United States ranked a relatively lowly 33rd while developing nations such as Guyana and Suriname came in at fifth and sixth respectively.

"The International Water Poverty Index demonstrates that it is not the amount of water resources available that determine poverty levels in a country, but the effectiveness of how you use those resources," she said.

"The links between poverty, social deprivation, environmental integrity, water availability and health becomes clearer in the WPI, enabling policy makers...to identify where problems exist and the appropriate measures to deal with their causes," she added.

Experts calculate that 20 percent of the world's population in a total of 30 countries faced water shortages in 2000, a figure expected to climb to 30 percent or 2.3 billion people in a total of 50 countries by 2025.

The Earth Summit in Johannesburg in September set the world a target of halving the number of people without access to clean water and sanitation by 2015.

It is a commitment due to be turned into concrete plans on March 22 at the Kyoto meeting which is already being flagged as likely to be the most important water conference ever held.

The World Health Organisation estimates that water-related infections hit more than three billion people every year, killing more than five million of them - mostly from diarrhoeal diseases.