Slamming Prime Minister Narendra Modi for his "bhrashtachari (corrupt) no. 1" taunt at Rajiv Gandhi, senior Congress leader Mallikarjuna Kharge said Monday Narendra Modi did not get "sanskar" (cultural grooming) as he had left home at a young age.
Mr Kharge said PM Modi's remark reflected his frustration.
At a rally in Uttar Pradesh Saturday, PM Modi attacked Congress chief Rahul Gandhi, saying, "Your father was termed Mr Clean by his courtiers but his life ended as bhrashtachari no. 1" (Corrupt no. 1).
Speaking to reporters in Karnataka's Kalaburagi, Mr Kharge said PM Modi lacked political and practical knowledge.
"He did not get sanskar at home as he had fled home at a young age. Where will he get it? People should have control over their tongue when speaking," the Congress leader said.
PM Modi's comment on Rajiv Gandhi has drawn widespread criticism from various opposition parties, which said he lowered the dignity of the office of the prime minister.
The BJP has countered the charge saying every word PM Modi said about the former PM was true. It received support from ally Shiromani Akali Dal.
Mr Kharge alleged that PM Modi always tried to rake up emotional issues and spoke lies.
Alleging that falsehood was a quality PM Modi has since birth, Mr Kharge said he had insulted a martyr who sacrificed his life for the unity of the nation.
"When Modi speaks so low about a person who gave his life for the nation, it means that he has no heart, no patriotism and his only objective is to win the election. It is unfortunate that the prime minister lacks the wisdom of what to talk and what not to talk. Except for talking, his contribution to the nation is nil," he alleged.
The Congress leader predicted victory in Amethi, Rae Bareli and elsewhere in Uttar Pradesh. Rahul Gandhi is contesting from Amethi and his mother Sonia Gandhi from Rae Bareli.