Fifteen months after forming the Pragatishil Indira Congress, Somen Mitra formally merged his party with the Trinamool Congress at a meeting in the Central Kolkata auditorium on Wednesday. Nearly 300 of Mitra’s followers accompanied him to the meeting where Trinamool chief Mamata Banerjee had sent party MP Sudip Bandopadhay to felicitate him.

Mitra had quit the Congress in July 2008 and was elected from Diamond Harbour constituency in the recent Lok Sabha polls on the Trinamool symbol.

Addressing the apprehensions of his supporters, who reportedly fear being sidelined in the Trinamool, Mitra said: “I will try to ensure that all of you get a post in the Trinamool Congress.”

On the reasons for the merger, Mitra said: “I am always in support of any anti-CPM combine. I had told top leaders of the Congress on several occasions to keep Mamata in their good books. But they never listened to me and therefore I quit today. The merger will strengthen Mamata’s hands to oust the CPM from power.”

Bandopadhay, who also left the Congress to join Trinamool last year, assured that the alliance between the Congress and Trinamool will work for the 2011 Assembly elections and 2010 Kolkata Municipal elections.