“What happened in Siliguri (where Congress formed municipal board with the help of the CPM) opened our eyes. We were hurt. Congress had earlier shared a government with the CPM . May be they are still hand-in-hand,” said Banerjee, who is the railway minister in the UPA government.

“Change is imminent. Congress or BJP, whoever tries to help the CPM will not succeed. The grand alliance of the people will dethrone the Marxists,” Banerjee said while welcoming Mukherjee, the former state Congress working president, who formally joined her party on Wednesday.

Mukherjee, who has been made senior vice-president of the Trinamool Congress and chairman of the party’s campaign committee for the civic polls, also minced no words in criticising his former party. “A conspiracy was hatched to break the electoral alliance between the two opposition parties and I believe CPM and Congress are involved in it,” said Mukherjee at the press conference where he was seated along side Mamata Banerjee.

Mukherjee, who was in-charge of Congress to oversee civic election, said: “I tried my best to keep both the parties together and to continue the electoral adjustment talks. But now, I am being compelled to say that the state Congress leadership broke the seat-sharing adjustment with Trinamool Congress.”

Stating that the Congress was defying the “desire and the demands” of the people in the state, Mukherjee said that much before the seat-sharing talks between the two parties had begun, five district Congress presidents had made public announcements that they would not give a single seat to the Trinamool Congress in their respective districts.

“Such announcements by the Congress leaders had vitiated the process of dialogue,” he added.

Later, Mamata Banerjee said that Mukherjee’s decision to join the Trinamool just ahead of the civic elections will “encourage hundreds of disgruntled Congress workers to quit the party”. In a strategic move, Mukherjee was seated beside former state Congress president Somen Mitra who too had left the party before the Lok Sabha polls and is now a Trinamool MP.