He also had a word of caution for the government seeking internal and foreign investment saying "capital is likely to be frightened away by conflict" and that "there can be no free market without freedom".
Singh also spoke of dangers to the republic if there was no unity and respect for diversity, secularism and pluralism.
"The assault or murder of thinkers for no more than disagreement with their views, or (of people) because of the food they eat, or their caste, cannot be justified on any grounds. Nor can the suppression of the right to dissent be allowed," he said in his inaugural address at a conference here ahead of the 125th birth anniversary of Jawaharlal Nehru.
The two-day meet is being held against the backdrop of Dadri lynching, beef row and other incidents. The incidents have triggered off an award-returning spree by litterateurs, artistes and film-makers.
The senior Congress leader said that all the right- thinking people have condemned such incidents in the strongest term as an "assault on the nation".