Here are the latest updates in the controversy
Netaji's nephew Ardhendu Bose, a former model and businessman, has said that his father believed the phones at their home in Mumbai were tapped.
He said this was taken as proof that the iconic leader didn't actually die in a plane crash in 1945. "My father never believed Netaji died in the plane crash," Mr Bose told NDTV.
Files declassified recently revealed that the Intelligence Bureau kept relatives of Netaji under close surveillance for two decades, mostly during the rule of Jawaharlal Nehru, the first prime minister of India.
Mr Bose said his family believed the only leader to be a "threat" to Jawaharlal Nehru was Subhas Chandra Bose. "If Netaji were really dead and perished in the air crash then why all this? Obviously there was some element of fact that Bose was alive, lurking around somewhere and would make an appearance," he said.
The declassified files have revealed that Netaji's close relatives, including his two nephews Sisir Kumar Bose and Amiya Nath Bose - sons of his brother Sarat Chandra Bose - were spied upon for 20 years between 1948 and 1968. Mr Nehru was Prime Minister for 16 of these 20 years.
Intelligence Bureau officials allegedly intercepted and copied letters written by the Bose family and even trailed them on foreign tours.
Netaji quit the Congress before Independence over differences with Mr Nehru and Mahatma Gandhi and launched an organised military resistance against the British after raising the Indian National Army. But he was said to have died on August 18, 1945, two years before India won freedom.
Netaji's death has been one of the most enduring mysteries in India's history and has been debated for decades. Ardhendu Bose said, "The conjecture is Subhas Bose was made to disappear in Siberia under the powers that be in India at that time."
Against the backdrop of the snooping controversy, Netaji's grandnephew Surya Kumar Bose is likely to meet Prime Minister Narendra Modi in Germany and demand declassification of all secret files related to the freedom fighter.
"Subhas Bose did not belong just to his direct family. He had himself said that the whole country is his family. I do not think it's just the duty of the family to raise this issue (of declassification of Netaji files)," Surya Kumar Bose, the president of the Indo-German Association in Hamburg, said.
Subhas Chandra Bose's Grandnephew On Kangana Ranaut's "1st PM" Claim Kangana Ranaut Says Subhas Chandra Bose Was "India's First PM", Internet Reacts Kangana Ranaut Calls Netaji "India's 1st PM", BRS Leader KTR Scoffs World's Largest Isolated Tribe Makes Rare Appearance In New Footage Why BJP Lost Lok Sabha Polls In Uttar Pradesh - 6 Reasons In Party Report "Re-Exam Only On Concrete Footing": Supreme Court On NEET-UG Row "Sell Golgappas?": Kangana Ranaut On Shankaracharya's Remark On E Shinde South Korea Court Grants State Benefits To Gay Couples In Landmark Ruling Did A Massive Dam In China Slowed Earth's Rotation? Truth Behind Viral Claim Track Latest News Live on NDTV.com and get news updates from India and around the world.