The move strengthens Banerjee’s front as Mitra enjoys a considerable clout in the state Congress. The decision comes when the Congress-led UPA government is to face a trust vote in the Parliament.

“I had no other option but to leave the party after serving it for 40 years. My new party will forge an alliance with the Trinamool,” said Mitra. He admitted that without Mamata it was difficult to oust the Left from the state.  

“I tried hard to bring the Congress and the Trinamool together. But Mamata is not ready to join hands with the Congress. People lost faith in the Congress after it allied with the CPM at the Centre,” he added. “Two names have been shortlisted for the new outfit — Progressive Indira Congress and Progressive West Bengal Congress,” added the rebel leader.

Mitra had earlier held two closed-door meetings with Banerjee. “Our discussions are on with Congress leaders. Those who want to join me are welcome,” he said. Asked whether his rift with Priya Ranjan Dasmunsi, WBPCC chief, caused this decision, Mitra said, “I have no grudge against anyone.”

Refusing to comment whether he will resign as a Congress MLA, he said, “I have not decided on it yet. My party will maintain equidistance from both the Congress and the BJP.” To become a separate political entity without inviting defection penalty, Mitra requires the support of six breakaway MLAs of the Congress.