West Bengal Congress president Adhir Ranjan Chowdhury on Thursday claimed that TMC supremo Mamata Banerjee is now endorsing the opposition INDIA bloc recognising its growing momentum and aiming to maintain her relevance in national politics.

Chowdhury's remark comes a day after Banerjee's announcement that her party will extend support to the opposition INDIA bloc from outside to form the government at the Centre.

Chowdhury termed Banerjee as an "opportunist politician" who altered her stance after realising the changing political landscape.

"This clearly indicates that the India alliance is striding ahead and on the verge of forming the government and that's is why as an astute and opportunist leader, Mamata Banerjee has decided to extend her support well in advance," Chowdhury told reporters.

"She (Banerjee) has lost her credibility. She has understood the crude reality that voters are gearing towards the INDIA bloc. She has realised that she has been isolated in national politics. This is a ploy to stay alive in national politics," he said.

Addressing a rally in Hooghly district on Wednesday, the TMC chief had said her party will extend support to the opposition INDIA bloc from outside to form the government at the Centre Banerjee, however, clarified that in West Bengal, her party will not support the Congress and CPI(M) and alleged that both the parties, who are part of the INDIA alliance, have joined hands and helping the BJP in the state.

"Do not count on the CPI(M) and the Congress in Bengal. They are not with us, they are with the BJP here. I am talking about that (INDIA bloc) in Delhi," she said.