Declassified CIA records provide ample indications the agency was able to infiltrate the top echelons of the Indian establishment in the 1960s as well. A case in point is a declassified November 1961 telegram. The name of the source is obviously not declassified. The telegram relays the gist of meetings between President Rajendra Prasad and Defense Minister Krishna Menon and between the President and Vice President Sarvepalli Radhakrishnan. A detailed report must have been filed later.
As per the telegram, President Prasad thought poorly of Menon's pro-USSR leanings. Radhakrishnan actually told the President that "this man (Menon) will have the whole world against us sooner or later." "If you believe so, tell the PriMin [Nehru]," Prasad replied testily.
It is not too surprising that the CIA should be keeping an eye on Menon who was a communist sympathiser and aspired to be Jawaharlal Nehru's successor. This surely had a lot of implication for the US's foreign policy during the Cold War. A 1951 agency report said: "The potential for [communist] infiltration of the [Indian] armed forces is probably enhanced by the fact that Defense Minister V. K. Krishna Menon is a member of the extreme left wing of the Congress Party and has associated with known Communists and fellow travelers. He is highly ambitious and would probably cooperate with and accept support from any group which might enhance his prospects for becoming Prime Minister."
What is startling is that the private discussions India's President had with the Vice-President and Defence Minister were leaked out. Whoever did it must have been very, very highly placed. You don't expect the President to speak his mind about a Cabinet minister in the company of ordinary folks.
The 1971 case cannot be an isolated one. There must have been within the official circles through the years several high-level moles, ensuring that the intelligence agencies of the world were well-supplied with the information not available from the open sources.