But two-thirds of the $470 million in compensation which majority plant owner Union Carbide paid over five years later still has to be disbursed by the Indian government, and no action has been taken against the company or its current owner, Dow Chemical Co.

"The disaster shocked the world and raised fundamental questions about corporate and government responsibility for industrial accidents that devastate human life and local environments," Amnesty said in a report, Clouds of Injustice.

"Yet 20 years on, the survivors still await just compensation, adequate medical assistance and treatment, and comprehensive economic and social rehabilitation," the human rights group said in an unusually hard hitting commentary.

It said the plant in the central Indian state of Madhya Pradesh, closed in December 1984 and lying derelict, had not been cleaned and was leaking poisons into the water supplies that the local population had no choice but to drink.

"Astonishingly, no one has been held to account for the leak and its appalling consequences," Amnesty added.

Union Carbide Corporation and its partner Union Carbide India Limited, and Dow Chemicals which took over UCC in 2001 have publicly stated they bear no responsibility for the leak, its consequences or the poisons still seeping into local wells.

Amnesty accused the firm of failing to tell medical authorities on the fatal night of Dec. 2, 1984 the name of the gas let alone the scale of the release.

It also accused the firm of still failing to provide full data on the cocktail of chemicals involved, and the Indian government of prematurely closing down a medical inquiry into the consequences and failing to keep a record of gas deaths.

"What happened at Bhopal was one of the worst industrial disasters ever witnessed. But it was not just a tragedy of the past, it has continued to be a tragedy ever since," Amnesty said.

It put the death toll at well over 20,000, against the Indian government's grudging acceptance of a figure of 15,000.

But the dead might be considered to be the lucky ones.

Hundreds of thousands of the survivors were suffering breathing problems, eye diseases, damaged immune systems, nerve damage, memory loss, cancer, miscarriages, gynaecological problems, impaired mental health and social exclusion.

Families had been plunged into debt because of the inability of the breadwinner to work full time due to health damage from the leak, and families who had since moved into the area were reporting health problems from drinking the water.

Amnesty urged the Indian government to provide safe water, force the site cleanup and make UCC and Dow come up with more money and information.