Rajinikanth said his party will contest all 234 seats of the state in the next assembly elections in 2021. The decision to contest the 2019 parliamentary elections will be taken at an appropriate time. His party, he said, would resign if it was unable to fulfil its electoral promises within three years of coming into power.

The actor said he was not entering politics to seek power. "The Chief Minister's post came to me long time ago, I kept away. I did not have the intention of getting the post of CM when I was in my 40s," Rajinikanth said. Over the last few days, posters came up in Chennai that say if Rajinikanth takes the political plunge, he would be the next chief minister.

The actor, who enjoys almost demigod status among his legion of followers, said he does not want cadres for his new party, but "watchdogs" who will rope in people from every village. "Until all this happens, none of us will criticise politics or politicians. At an appropriate time before assembly polls, we shall explain our policies," he said.

The BJP, which had given Rajinikanth an open offer to join, on Sunday congratulated him. State party leader T Soundararajan tweeted: "Welcome actor Rajinikanths political entry with motto of corruption free good governance which is the sole aim of BJP". Earlier party chief Amit Shah has said Rajinikanth was welcome to join the party and Prime Minister Narendra Modi had met him during a visit to Chennai last month.

The death of Jayalalithaa unleashed a power struggle within the ruling AIADMK over the last year that saw a split between Chief Minister E Palaniswami and his predecessor O Panneerselvam, a patch-up between the two factions, and then a loss in the RK Nagar by-election.

The merged AIADMK lost the RK Nagar seat, represented by Jayalalithaa, to sidelined rebel TTV Dhinakaran, the nephew of Jayalalithaa's closest aide VK Sasikala, who had laid claim on the legacy of the former Chief Minister.

Kamal Haasan, who announced his political ambitions last month, had challenged the ruling party for weeks, accusing it of corruption and bad governance and promised a whistle-blower app by January. This morning, he tweeted: "I greet Rajini's social concern and political debut. Welcome welcome," his tweet read.

Rajinikanth, who had not been so openly critical, was cryptic about his plans. His pronouncement in May - "If God wills it, I will enter politics tomorrow" - had led to a frenzy.

Earlier this week, the actor, whose fans call him "Thalaivar" or "Ultimate Boss", had given the strongest indication of his plans, saying entry into politics needed a winning strategy.