Singh urged the prime minister to show "maturity and gravitas, as expected of the high office he holds, instead of concentrating his energy exclusively on scoring "erroneously conceived brownie points".
In a sharp counter-offensive, the former PM said that Modi was setting a "dangerous precedent" with his "ill-thought transgression" and asked him to apologise to the nation.
"The discussion was confined to Indo-Pakistan relations".
Former foreign minister Khurshid Kasuri, accused along with Congress leaders of collusion, said he's even met the head of India's intelligence agency but that doesn't mean they are hatching a conspiracy.
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.
During the event, PM recalled the initial times of FICCI's founding in 1927 and said, "A similar atmosphere exists today when people of the country are coming forward to fulfil their responsibilities towards the nation".
Prime Minister Narendra Modi on Wednesday launched a blistering attack on the previous Congress-led UPA regime, saying that banks were pressured to give loans worth thousands of crores of rupees to select industrialists in a scam bigger than 2G, coal and Commonwealth Games scams.
"When it comes to respected Manmohan Singh ji's honesty, I would not like to say anything".
Congress president-elect Rahul Gandhi, who returned to the national capital from the poll-bound Gujarat after a hectic election campaign, was also present at the Parliament to pay his tributes to those who lost their lives in the 2001 attack. "The monumental loot and plunder under his watch speak for him in abundance!", Shah tweeted.
In a video message posted on Twitter, Singh accused Modi of spreading "falsehood and canards" to score political points and seeking an apology for his "ill-thought transgression".