He was 92 and is survived by his daughters U Vasuki, a CPM state secretariat member, and Nirmala Rani, a lawyer.
Umanath was born in Kozhikode, Kerala, in 1922 and shifted to Chennai during his student days. He was elected to the Tamil Nadu legislative assembly as a CPM candidate from Nagapattinam constituency twice (in 1977 and 1980).
He served as a Lok Sabha member for two terms. He was elected to the third and fourth Lok Sabhas from the Puddukottai constituency.
A trade union leader for many years, Umanath was also a former Tamil Nadu state committee secretary of the CPM.
His wife, Papa Umanath, one of the founders of the All India Democratic Women's Association (AIDWA) died in 2010 at the age of 80.