Chief Minister Pinarayi Vijayan said 83-year-old Mani's record has no parallel either in the assembly or even in the Lok Sabha.
"Governments came and went, but Mani was always there in the assembly', Vijayan said.
Mani also holds the distinction of being the longest serving minister,who has presented 13 budgets in the assembly.
Speaker P Sreeramakrishnan wished the Kerala Congress(M) supremo for completing half a century as member of the house.
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Describing him as a phenomena, Former Chief Minister Oommen Chandy said Mani surprised everyone with his efficiency and calibre, while Opposition leader Ramesh Chennithala said the occasion was that of 'pride' and 'happiness'.
He had represented Pala in Kottayam district since its formation in 1965.
Mani's illustrious legislative career was marred by allegations in 2015 when a section of bar owners alleged that he had demanded bribe for reopening closed pubs.
Mani resigned from the UDF ministry following the bar bribery charges.
KC(M), a former partner in the Congress led UDF, had severed its 30-year-old ties in 2016 following differences with the lead partner Congress.
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