By Sanjoy Majumder
BBC News, Delhi
In a file photo from 1974, a crater is shown in the Thar desert area southwest of New Delhi where India conducted an underground nuclear test. India successfully tested three devices in the same area on Monday May 11,1998. (AP Photo/HO)
India's nuclear tests shocked the world
A retired atomic scientist who was closely associated with India's 1998 nuclear tests has said they were not as successful as was claimed.
K Santhanam said one of the tests - on a hydrogen bomb - had not worked, and that India would have to carry out more tests for a credible nuclear deterrent.
His statement has been dismissed by the government and his former colleagues.
The Indian tests led to similar tests by Pakistan, raising fears of a nuclear conflict between the two countries.
Cover-up?
K Santhanam is a respected Indian atomic scientist who was project director of the 1998 nuclear tests.
He now says that one of the five tests that were carried out, in which a thermonuclear device or hydrogen bomb was detonated, did not perform as well as expected.
He also said that everyone associated with the tests immediately recognized that something had gone wrong.
If his statement is accurate it points to a massive cover-up by India and also confirms what many in the West suspected at the time - that the nuclear devices India tested were not as powerful as had been thought.