TMC leader and West Bengal minister Partha Chatterjee said Roy, who is a Rajya Sabha MP, had been attempting to 'weaken the party' for quite some time.
Roy has resigned from from the party and the Rajya Sabha, reports said.
Addressing a press conference on Monday, Roy said, "With a heavy heart, I am announcing that I will quit the primary party post of Trinamool Congress and the Rajya Sabha membership. I will formally resign after the Durga Puja vacation."
Roy, one of the founding leaders of the Trinamool Congress, had long been regarded the second-in-command of the party after Mamata Banerjee
and the architect of TMC's organisational and electoral success in the state.
However, he fell from the grace of Banerjee following his interrogation by the CBI in connection with the multi-crore Sarada chit fund scam.
His party believed that Roy, being the chief fund manager of TMC was spared further trouble after he parted with some secrets that could be used as a weapon by the BJP against the Trinamool Congress.
For quite sometime rumours were doing rounds that he has been in close touch with the BJP's top leadership and is likely to join the party.
However, neither Roy nor the BJP has so far confirmed it.
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