It was under his stewardship that Kerala signed on for continuing with the Mullaperiar Dam agreement with Tamil Nadu, as a part of reviewing the pre-independence agreement between the Kingdom of Travancore and the Madras Presidency. This agreement, experts on the subject believe, fretted away the interests of Kerala and became the prime reason for unenviable situation that Kerala finds itself today in the Mullaperiar issue. He was not a member of the Kerala Assembly then, but subsequently got elected from Kottarakkara in the by-election held in April 1970. In the mid-term poll conducted in 1970, he was again elected this time from Kodakara in Thrissur District and was sworn in as Chief Minister on 4 October 1970 and held office till 1977.