The sharply-worded attack was virtually the same as the written statement that the 86-year-old Congress leader had released on Monday following Modi's remarks insinuating that Singh had colluded with Pakistan in the Gujarat polls.
"Fearing imminent defeat in Gujarat, desperation of Prime Minister to hurl every abuse and latch on to every straw is palpable," Singh said in the message released to TV stations.
The campaign was marked by a fiesty and often acrimonious speeches where Modi and Congress president-elect Rahul Gandhi locked horns repeatedly.
"I am deeply pained and anguished by the falsehood and canards being spread to score political points in a lost cause by none less than Prime Minister Narendra Modi," he said and demanded an apology.
Also Read
"We are seeing a very angry Manmohan Singh ji these days. We just want to ask him whether he was so angry when monumental loot and plunder was happening under his watch? The nation missed his anger then!" Shah tweeted.
Singh urged the prime minister to show "maturity and gravitas, as expected of the high office he holds, instead of concentrating his energy solely on scoring "erroneously conceived brownie points".
Strongly rejecting the "innuendos and falsehoods" made by Modi, Singh said he did not discuss Gujarat elections with anyone else at the dinner hosted by Congress leader Mani Shankar Aiyar as alleged by Modi and nor was the Gujarat issue raised by anyone else present at the dinner.
"The discussion was confined to Indo-Pakistan relations. It is wrong and unfair to question nationalism of journalists, diplomatics and public servants present at the dinner," he said.
The Congress Party needs no sermons on "nationalism" from a party and prime minister, whose compromised track record on fighting terrorism is well known, he added.
Pointing out that Modi had gone to Pakistan uninvited after the terrorist attacks in Udhampur and Gurdaspur, Singh said "let him also tell the country the reason for inviting the infamous ISI of Pakistan to our strategic Air Base in Pathankot to investigate a terror attack that emanated from Pakistan.
Disclaimer: No Business Standard Journalist was involved in creation of this content