The minister went further and said democracy is "safe" in the country as long as Hindus remain in majority.
He said social harmony and development would be "in danger" the day the population of the majority community starts decreasing.
Delivering a lecture here, the minister said nationalism was in a "kind of danger" due to demographic changes.
"...Democracy is safe in the country as long as majority (Hindu) population is there. The day the population of the majority community starts decreasing, the democracy, development and social harmony will be in danger," he said at the lecture on nationalism.
"Hindu population has dipped in 54 districts in states like Uttar Pradesh, Assam, West Bengal, Kerala, besides some other states. These districts are Muslim majority and this demographic change is a threat to the unity and integrity of the country," the BJP leader said.
He said a family planning law for all faiths should be enacted.
"...With all responsibility I say that the social harmony has taken a beating and nationalism has declined (in areas) where the population of Hindus has declined," he said.
While population of Muslims has increased considerably in India, the number of Hindus has fallen drastically in Pakistan after the Partition.