Congress leader Rahul Gandhi promptly admonished Aiyar, who has often courted controversy with his off-the-cuff comments, prompting the senior leader to apologise.
Modi, who was on campaign trail in the Patidar belt of Surat in poll-bound Gujarat, quickly seized on the comments that may prove potentially damaging for the Congress coming as it did on the last day of electioneering for the first phase of poll in the state on December 9, insisting he was targeted over his caste.
"He (Modi) is 'neech kism ka aadmi' (a vile man) who has no 'sabhyata' (civility)," Aiyar said, attacking Modi after the latter accused the Congress of seeking votes in B R Ambedkar's but trying to erase his contribution to nation building.
Modi quickly lapped up Aiyar's comment to launch a scalding attack on the Congress leader and his party.
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"This is a Mughal mentality where if such a person (who comes from a humble background) wears good clothes in a village, they have a problem," he said.
Modi said he was following in the footsteps of Mahatma Gandhi who devoted his entire his life to the cause of poor and the "neech" (people of the lower strata of society". "I am sitting with the 'neech' and will continue doing so even if you find me vile, my caste low," he said.
"BJP and PM routinely use filthy language to attack the Congress party. The Congress has a different culture and heritage. I do not appreciate the tone and language used by Mr Mani Shankar Aiyer to address the PM. Both the Congress and I expect him to apologise for what he said," Gandhi said on Twitter.
Chastised, Aiyar was soon on national television proffering clarification, insisting it was because of his poor understanding of Hindi language that he used the word, and tendering apology.
"Therefore, for the misinterpretation that can be given to the word, I extend my apologies, particularly since it is going to harm the Congress party's interests in Gujarat," he said.
Aiyar said he was asked about Modi's criticism of the Congress at an event and "the bulk of my answer dealt with Modi's very, very nasty remarks about the Congress party and Dr Ambedkar and I used the word 'neech'."
When repeatedly asked if he was tendering apology for calling Modi 'neech', Aiyar said,"Do I apologise about the word 'low'? No. Do I apologise about the word that is translated which says 'low born'? Absolutely yes."
The Congress leader said he does not think Modi was low born "but the language...I would say is very low".
Modi, at his rally in Surat, which has a sizeable population of Patidars, a section of whom are on a warpath with the government over reservation for the community, said people will give a befitting reply to the Congress through the ballot box.
"The Congress party has challenged the weaker and backward sections of India by calling the Prime Minister as neech. The strength of Indias democracy will be displayed when a person of humble background politically defeats the dynasty and its representatives," he said.
BJP Chief Amit Shah said he was neither shocked nor surprised by Aiyar calling the prime minister neech.
"Yamraj, Maut Ka Saudagar, Ravan, Gandi Nali Ka Keeda, Monkey, Rabies Victim, Virus, Bhasmasur, Gangu Teli and Goon. These are some words or phrases Congress has used for PM @narendramodi in the past. Not much has changed. We wish them well. We will continue to serve 125 crore Indians," he tweeted.
His 'chaiwala' barb against Modi ahead of the 2014 Lok Sabha polls gave the then BJP's prime ministerial candidate a stick to beat the Congress how with, as election results showed.
In 1998, he had called the then prime minister Atal Bihari Vajpayee, a widely respected leader, 'nalayak' (incompetent), a Hindi word considered a pejorative. Aiyar apologised after the backlash.
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