"Modi is like a scorpion sitting on a Shivling. You cannot remove him with your hand and you cannot hit it with a 'chappal' (slipper) either," said Tharoor at a literary event, recalling what an RSS member had told a journalist in 2012.

Participating in the Bengaluru Literary Festival, Tharoor referred to the metaphor in the context of his latest book, "The Paradoxical Prime Minister", and alleged that Modi's personality cult did not go down well with many in the Rashtriya Swayamsevak Sangh (RSS).

"There is an extraordinarily striking metaphor expressed by an unnamed RSS source to journalist Vinod Jose of 'The Caravan', who expressed their frustration with their inability to curb Modi," said Tharoor in his speech at the literary festival.

The remark by the RSS source depicted the "complex" dynamics that exist between the "Hindutva movement and the Moditva expression of it", Tharoor added.

Union Law Minister Ravi Shankar Prasad condemned Tharoor's remarks and said the Congress leader had disrespected Lord Shiva.

"Shashi Tharoor, who is accused in a murder case, has attempted to disrespect Lord Shiva. I seek a reply from Rahul Gandhi who claims himself to be a 'bhakt' (devotee) of Lord Shiva on this horrific denunciation of Hindu gods by a Congress MP. Rahul Gandhi must apologize to all Hindus," Prasad said in a tweet.

Responding to Prasad, Tharoor said that his comment quoting an unnamed RSS source on Modi had been in public domain for six years.

"This comment (not by me) has been in the public domain for six years. R.S. Prasad making an issue of a six-year-old quote shows how little new the BJP has to offer the nation," tweeted Tharoor.

Clarifying, Tharoor said he had cited in his book the context in which it (metaphor) was used.

"In view of the unseemly demonisation of an out-of-context remark today involving a scorpion metaphor, my book #TheParadoxicalPrimeMinister cites and footnotes in this article -- please see the last paragraph of this article," tweeted Tharoor, sharing the link to "The Caravan" article in 2012, which quotes an RSS leader using the scorpion metaphor to describe Modi.