"The UPA-Left Coordination Committee was formed for exchange of opinion between the government and the left parties on major policies. But it has now virtually turned into an ineffective and defunct body," CPI(M) politburo member and Left Front chairman Biman Bose said.

Asked if his party would follow in the footsteps of the RSP, Bose said, "it is the same whether to remain in the UPA or not."

Forward Bloc state secretary Ashok Ghosh said "the RSP's decision is not unjust as it was taken after a assessment of the situation in their own party."

He, however, said that it would weaken the Left Front not only in West Bengal, where it has suffered reverses in the panchayat elections, but also in the country "at a critical time".

Senior CPI leader and West Bengal Water Investigation minister Nandagopal Bhattacharya termed RSP's move as "unexpected".

"We are unaware of such a decision by the RSP. If it is true, it is definitely unexpected as we take such decisions together," he said.