Two recently de-classified Intelligence Bureau files reveal that former prime minister Jawaharlal Nehru spied on the family of freedom fighter Netaji Subhash Chandra Bose for two decades from 1948 to 1968.

Nehru died on May 27, 1964, but the spying continued for four years even after his death.

Apart from allegedly intercepting and copying letters written by Bose's family members, the agency sleuths shadowed them on their domestic and foreign travels.

The agency seemed especially keen to know to whom Bose's family met and their discussion.

Bharatiya Janata Party leader MJ Akbar claimed that the government was unsure whether Bose was dead.

Akbar said Bose was the only charismatic leader who could have mobilised and united the opposition parties against Congress, and offer it a serious challenge in the 1957 elections.