"I did not like the functioning of the party. There was no intra-party democracy. The party elections was not conducted the way it should be," he told reporters after formally joining the BJP, which has set eyes on strengthening its presence in Tamil Nadu ahead of 2016 Assembly elections.
The actor-turned politician said he had the blessings of former Union minister M K Alagiri, elder son of DMK chief M Karunanidhi.
Napoleon is the third prominent person to join the BJP during Shah's two-day tour of the state. Lyricist Gangai Amaran and choreographer Gayathri Raguram joined the party yesterday.
BJP, which led a rainbow alliance of smaller parties in the Lok Sabha elections, has been seeking to position itself as an alternative to the Dravidian majors DMK and AIADMK, accusing both of neglecting the development of the state.
More From This Section
Napoleon, who was Minister of State for Social Justice and Empowerment in the UPA Government between 2009 and 2012, had been sidelined in DMK for supporting Alagiri, who was removed from the party earlier this year.
Hailing Narendra Modi as a "visionary" for the country, he said his entry into BJP was to strengthen the Prime Minister's hands in every deed.
On a query about Alagiri's brother and DMK Treasurer M K Stalin, he said, "I do not have any opinion against any individual."
In a letter to the DMK President and General Secretary, Napoleon had said he was quitting the party and thanked those who supported him. However, he did not mention any reasons for his decision.