A day after Mr Modi's remarks sparked a political furore, Mr Singh said on Twitter, "Shouldn't we all be Nationalist Indians rather than Hindu Nationalist or Muslim Nationalist or Sikh Nationalist or Christian Nationalist ?" (Who said what)
In another tweet, he also took a jibe at Sangh Parivar saying, "Don't divide this Great Nation on basis of religion which Savarkar and Jinnah did. They were the original authors of Two Nation theory."
Hitting out at fundamentalism in all forms, he praised Pakistani teen activist Malala Yousafzai's speech at the United Nations, who was shot by Taliban last year.
"What a powerful condemnation of Taliban and all forms Fundamentalism. She has now become an Icon for World Literacy. Congratulations to her and let us resolve to fight for all that she stands for! May God give her a long life and the strength she deserves," the Congress general secretary said.
The tweets by Mr Singh, a known detractor of the controversial Gujarat Chief Minister, came a day after Mr Modi's attempts to defend himself against allegations of inaction during the 2002 riots in Gujarat.
"Even If I am in the back seat of a car and a puppy (kutte ka bachcha) comes under the wheels, isn't it painful? It is. Whether I am a chief minister or not, I am a human being. I will be sad if something bad happens anywhere," Mr Modi was quoted as saying in an interview aired yesterday. (Read: Modi's full interview here)
The Gujarat chief minister said he had done "absolutely the right thing" during the 2002 riots and that his government had used its "full strength" to set things in order.
"I am nationalist. I'm patriotic. Nothing is wrong. I am born Hindu. Nothing is wrong. So I'm a Hindu nationalist. So yes, you can say I'm a Hindu nationalist because I'm a born Hindu," he had said.