The veteran Kerala Congress leader had been a dominant player in Kerala's coalition politics, serving under six chief ministers.
Kerala Congress veteran and former state finance minister K M Mani died at a private hospital on Tuesday, hospital sources said.
He was 86.
He is survived by his wife, Annamma Mani and six children, one son and five daughters.
Mani, who had been undergoing treatment at the VPS Lakeshore hospital for pulmonary disease, breathed his last at 4.57 PM, they said.
Mani had been suffering from COPD (Chronic Obstructive pulmonary disease) for several years and had frequently been hospitalised for chest infection.
He had been an MLA of Pala assembly constituency for nearly five decades.
Prime Minister Narendra Modi expressed grief over the death of Mani and said his rich contributions to the state would be remembered.
In a tweet, Modi said "Shri KM Mani was a stalwart of Kerala politics. His impeccable electoral record indicated his deep connect with the citizens of the State. His rich contribution to the state will be remembered. Pained by his demise. Condolences to his family and supporters. RIP."
Kerala Congress-Mani is a key ally of the Congress-led United Democratic Front in the state.
Mani fell ill days after declaring his close confidante and Kerala Congress-M leader Thomas Chazhikadan as the UDF candidate in Kottayam Lok Sabha seat.
His son and KC-M leader Jose K Mani is a member of the Rajya Sabha.
The veteran Kerala Congress leader had been a dominant player in Kerala's coalition politics, serving under six chief ministers.
Mani, a successful practitioner of pragmatic politics, had handled key portfolios like finance for most Congress-led UDF governments, which came to power alternatively since the late 1970s.
He also had brief stint as a minister in the Communist Party of India-Marxist-led Left Democratic Front ministry in early 1980s.
A man of wit and humour, Mani, who was elected to the Kerala legislative assembly for the first time in 1965 from Pala constituency of Kottayam district, never lost an election and continued to represent the constituency till his death.
He held several key portfolios, including home affairs, finance and law, irrigation and law, revenue and law in various ministries headed by stalwarts in Kerala politics including C Achutha Menon, P K Vasudevan Nair, K Karunakaran, E K Nayanar, A K Antony and Oommen Chandy.
Mani had been a minister for 24 years in various ministries and as the finance minister, presented 13 budgets in the state assembly.
His foes in the Kerala Congress politics have always accused him of engineering splits in the regional party for his political benefits.
About the phenomenon of frequent splits in the Kerala Congress and emergence of Kerala Congress with varying suffixes, Mani oncefamously said: "We are a party that splits as we grow and grows as we split".
A lawyer by profession, Mani wielded considerable clout among people of the Syrian Catholic community in Kottayam and Idukki districts, ever since he emerged as a powerful leader in the 1970s in the Kerala Congress, which has its roots among the farmers in the erstwhile Travancore region.
Mani-led Kerala Congress-M is the largest among nearly nine political outfits having the name of Kerala Congress with varying suffixes and is the third largest constituent in the Congress-led UDF in the state.
He was forced to quit as finance minister from the Chandy-led government in November 2015 following the Kerala high courts observations against him in the bar bribery case, casting a shadow over his career.
Born as the son of a farmer at Marangattupalli village near Pala, Mani completed his Bachelors Degree in Law and started practicing as an advocate at Kozhikode as a junior of P Govinda Menon, who later became Judge of Kerala high court.
Beginning his political career as a Congress worker, Mani had served as the general secretary of Kottayam District Congress Committee before becoming part of the Kerala Congress movement, headed by stalwarts like K M George.
He authored several books, including Fiscal Problems of Kerala-Causes and Remedial Measures, The People's Socialism, The Eighth Five year Plan-an Alternative Approach, Doctrine of Toiling Class, The Economic Development of Kerala, Toiling Class Theory and Political and Economic Studies.
