He was a member of Dravida Munnetra Kazhagam party in Tamil Nadu until being expelled for alleged anti-party activities on 30 July 2009.
He was also former Minister for Animal Husbandry and Minister for Housing & Urban Development in the AIADMK government after the 2001 election.After his expulsion from the AIADMK, Radhakrishnan accepted an invitation to join the Dravida Munnetra Kazhagam.
Even though there was an anti-incumbency wave against the DMK, he won the 2011 Assembly election in Tiruchendur constituency.On 14 May 2015, Radhakrishnan was suspended by the DMK after he and A.
Soundara Pandian greeted AIADMK leader Jayalalithaa after she was acquitted in the disproportionate asset case against her.In the elections of 2016, Radhakrishnan won again in Tiruchendur, beating Sarath Kumar of the AIADMK.