Former Union home minister Buta Singh rejoined the Congress on Friday, nearly 18 months after he quit the party to contest the 2014 Lok Sabha elections as an independent from Jalore in Rajasthan.
Singh, 81, also heads Safai Mazdoor Congress, an organisation working for the welfare of sanitation workers.
He was welcomed into the Congress fold by senior leaders Ajay Maken and PC Chacko.
Singh, who hails from Jalandhar in Punjab, served as Union agriculture minister in the Rajiv Gandhi government between 1984 and 1986.
He was the home minister from 1986 to 1989.
Singh was elected to the Lok Sabha eight times between 1962 and 2004.
Singh was also Bihar governor from 2004 to 2006 during the UPA 1 government. He was also the chairman of the National Commission for Scheduled Castes between 2007 and 2010.