Kolkata: In what could add to the Trinamool Congress' growing political challenges, senior leader and MLA Madan Mitra on Wednesday announced his resignation from the party's organisational posts and joined the rebel Trinamool Congress faction led by Ritabrata Banerjee.

The veteran leader, however, clarified that he has not resigned as an MLA.

Announcing his decision, Mitra alleged that he had earlier advised TMC national general secretary Abhishek Banerjee to step away from the party's affairs for a temporary period so that senior leaders could rebuild and strengthen the organisation.

"I had suggested to Abhishek Banerjee that he should leave the party for six months or a year. I had told him to let us strengthen the party, and then you can come back and take your place. But he refused. He said he would not leave the party," Mitra said.

Launching a sharp attack on the party's leadership, Mitra claimed the Trinamool Congress was losing ground and facing a serious crisis.

"The party is sinking, the boat has already sunk. People are dying... the party belongs to everyone... I have resigned from all positions. However, I am still an MLA," he said.

Mitra's exit is likely to trigger fresh political debate in West Bengal, with the move coming as the ruling Trinamool Congress faces renewed scrutiny over internal differences. A prominent face of the party for years, Mitra's decision to join the rival Trinamool faction is expected to be viewed as another setback for Mamata Banerjee.