Former Kerala Minister and Congress (M) chairman, KM Mani passed away today at the age of 86. He was considered as the doyen of modern politics. Mani passed away at a city hospital in Kochi, where he was udergoing treatment for a respiratory-related illnesses. The hospital's medical bulletin said Mani had been suffering from Chronic Obstructive Pulmonary Disease (COPD) for a number of years and also had an acute chest infection. KM Mani, better known as Mani Sir, was an important ally of Congress in Kerala and one of the most popular politicians in the state. Leaders of different political parties and his followers visited the hospital on Tuesday to pay homage. Mani's body will be taken to his home town tomorrow where his friends and followers will be able to pay their last respects. The funeral will be held on Thursday at 2pm at the cemetry in St Thomas Cathedral, Pala. Offering his sympathies, Prime Minister Narendra Modi said on Twitter, "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." Former PM Manmohan Singh condoled the death of KM Mani, calling it a loss to the country. Mani enjoyed a career that spanned 54 years, and served as Kerala's Finance Minister. He was also India's longest-serving legislator and represented his constituency without a break till his death. KM Mani represented Pala, his native place, in Kottayam beginning from 1965. The 86-year-old had great influence, particularly among entrepreneurial Catholic classes in central Kerala districts. At one point of time, he was one of the most sought after ally for both communists-led Left Democratic Front and Congress-led United Democratic Front.