He was also very critical of the book written by veteran journalist Kuldip Nayar, which blamed late Rao for the demolition of Babri mosque on the basis of a reported claim by socialist leader Madhu Limaye.
Lamenting that "vested interests" were trying to spew venom at his late father, P V Ranga Rao said the former Prime Minister's family was "very unhappy and sad" about it.
"What is being written in these books is not fair to father. We don't expect such things about a person who is no more," Ranga Rao said.
"How can anyone talk something ill about a person who is no more...A person who cannot defend himself?," Rao said reacting to the claims made in late Congress leader Arjun's soon-to-be-released posthumous autobiography 'A Grain of Sand in the Hourglass of Time'.
In the book, Singh had quoted P V Narasimha Rao as saying, "Why should Congress party be hitched to the Nehru-Gandhi family like train compartments to the engine" when a suggestion was made that Sonia be made Congress chief after the assassination of her husband Rajiv Gandhi in May, 1991.
Ranga Rao, who is an MLC, countered the claim saying his father always remained "very loyal" to the Nehru-Gandhi family and in fact was the first person to take Sonia's name for the post of the Prime Minister after Rajiv Gandhi's death.
"Father himself wanted Sonia to lead the party and become Prime Minister. But she declined," he recalled.
Ranga Rao also trashed as "unbelievable and untenable" the contention in Nayar's soon-to-be released autobiography "Beyond the Lines" that Narasimha Rao "connived with saffron forces" to let the Babri structure demolished, a reported claim by Limaye.
