Singh said Modi could not be accused of directing killings during the 2002 riots and allegations in this regard would have caused him immense "mental trauma".
Releasing a book on Modi here, he said that "in independent India if there is one politician most targeted, his name is Narendra Modi. All kinds of allegations have been levelled against him."
Referring to some of the charges levelled against Modi, he said, "It was alleged that he (Modi) said fire as many bullets for 24 hours, kill as many as you can ... I have been a CM and can say with confidence that no CM ever wants that an anarchy-like situation develop on his watch."
Singh has served as chief minister of Uttar Pradesh. "How much mental trauma and pressure he would have faced, you can imagine," he said at the function which was attended by foreign diplomats among others.
While seeking to defend Modi on the issue of riots, the BJP chief said thousands of riots have happened in India and mentioned communal violence that occurred in Gujarat before 2002 and Assam during the rule of Congress.
Showering praise on the Gujarat chief minister, he said that when he announced Modi's name as the party's prime ministerial candidate, he was merely making an announcement of a consensus already reached within the party.
Modi had shown "excellence in organisation, administration and socio-economic measures and such a man cannot be an ordinary talent," he said.
"His critics say all the development is no wonder for somebody ruling a relatively small state for the last 10-12 years. I ask them what happened to West Bengal where the Left ruled for close to 35 years. What about Bihar where Lalu ruled for 15 years," he said.
Singh said UPA government had declared Gujarat as the best state in the implementation of its 20-point programme and a Congress research team from the US, which he noted had denied him a visa, has also praised his performance.