Talking to reporters here, Former CPI(M) MP Sivaraman said that he decided to leave the Congress party in protest against what he alleged the "corrupt governance" of the UDF government in the state.
He also stepped down as the chairman of State Development Corporation of Scheduled Caste.
Sivaraman had been elected to the Lok Sabha from Ottappalam reserved constituency on a CPI(M) ticket in the 1993 bypoll, which was necessitated after former President K R Narayayan quit the seat to contest as Vice-President.
He later joined Congress in February 2010 following differences with the Left leadership.
Sivaraman, however, was not in good terms with Congress leaders in recent times, party sources said.
Sivaraman also said that he wanted to return to his former party, CPI(M).