Kolkata, May 11 -- The Congress, the Left front and the CPI-ML (Liberation) on Sunday rejected an offer by Trinamool Congress chief Mamata Banerjee to form a united platform against the Bharatiya Janata Party. "Absolutely not. We will not accept anyone identified as criminal, extortionist, corrupt and communal. We will stand by people and the marginal population," CPI(M) state secretary Md Salim said in a reply to the proposal Banerjee made on Saturday even though his party is not in power in any state for the first time in 49 years, having lost the Kerala polls. State Congress spokesperson Soumya Aich Roy said, "We can't believe our ears. You (Banerjee) invited national parties, indicating the Congress, Left and the ultra-Left to join you....