Iyer, who had been admitted to hospital for nearly a fortnight, was suffering from renal and cardiac failure and neumonia, hospital sources said. He had stopped taking food and was on a liquid diet since Monday.
On November 15, his 100th birthday was celebrated in Kochi, where had been residing. Iyer was active as a human rights activist too.In past many years, Iyer has spearheaded many mass movements in the state. He also headed the Kerala Janakeeya Prathirodha Samithi, a citizen's collective in Kerala.
A Brahmin by birth, Iyer led a secular life. Iyer has also penned over 100 books on subjects ranging from legal matters to social issues.
Iyer served as a minister in the first communist government in India which was formed in Kerala under E M S Namboodiripad in 1957. As a minister, he implemented the revolutionary Kerala Land Reforms Act.
In 1959, after the government was dissolved, Iyer took up legal profession and starting practice as an advocate in the Kerala High Court. In 1968, he joined the High Court as a judge. In 1973, Iyer was appointed as a Supreme Court judge. He retired as SC judge in 1980.
He was part of the citizen's panel that investigated the Gujarat riots in 2002.
The country honoured him with a Padma Vibushan in 1999.