Banerjee explained during an internal party meeting that the TMC, which won 211 seats, could have won 10-12 seats more had there been no "infighting".
A senior TMC leader told PTI wishing to remain incognito that Banerjee came down heavily on leaders of Nadia and Malda districts for poor results.
"She had said that if TMC could perform well in Murshidabad, then why did it fail in Malda. She also criticized the Nadia district leadership for performing poorly," the leader said.
Banerjee told the party meeting that the new committee would identify the reasons for defeat in the seats which it had expected to win.
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The report would be submitted in the next few days, the leader said.
The Chief Minister said that the TMC observer for Nadia district would be Abhishek Banerjee, her nephew. The Malda district committee of the party would stand dissolved.
The eight ministers who lost are Krishnendu Narayan Chowdhury, Chandrima Bhattacharya, Manish Gupta, Sankar Chakraborty, Sabitri Mitra, Abdul Karim Chowdhury, Shyamapada Mukherjee and Upendranath Biswas.
Meanwhile, TMC MP and former Railway Minister Dinesh Trivedi, who had embarrassed his party be making uncomfortable comments during the Narada sting operation, was absent at the internal meeting attended by all MPs.