"It is distressing to see that this document -- the foundation of our country, given to us by Congress and Ambedkar (Bhimrao Ambedkar) -- is under attack. Attacks are being directly and surreptitiously made by senior members of the BJP," Mr Gandhi said during the Congress Foundation Day celebrations.
"What is happening in our country is a web of deceit. BJP operates on the basic idea that a lie can be used for political benefits.
"Central idea of the Congress party is the truth -- we accept the truth, we work for the truth and we fight for it," he said, adding: "That is the difference between us and them."
He said the formation of the Constitution was one of the most important moments in the history of the nation. "It was the day we decided that every Indian, regardless of colour, caste or religion, is going to have the same importance, the same rights.
"Our duty is to defend the rights and future of ever single citizen.
"We might suffer but we will not give up. We will defend the truth," he said.