Mr. Raghavan (81) was keeping indifferent health for quite some time, they said.
Once a firebrand CPI (M) leader, Mr. Raghavan quit the party and floated the CMP following differences with the leadership in the mid-1980s.
Since then he had been with the Congress-led UDF and became a Minister twice, handling the Co-operation portfolio.
Recently, a faction in the CMP pulled out of the UDF and moved closer to the LDF.
Mr. Raghavan had been bed-ridden for the last two years due to various ailments.
He is survived by wife Janaki, a daughter and three sons, one of whom M.V. Girish Kumar is a journalist.