Viduthalai Chiruthaigal Katchi (VCK) and Puthiya Tamizhagam said the present coalition was already "strong" but they are open to others joining them.
VCK leader Thol Tirumavalavan said if Karunanidhi wanted more parties to join the alliance, "it is welcome".
Puthia Tamizhagam's leader K Krishnaswamy made a similar statement on the matter.
Hitting out at Jayalalithaa, Krishnaswamy and Manithaneya Makkal Katchi leader Jawaharillah Khan said they left the AIADMK alliance as "it was not possible to meet the party chief even to convey the grievance of the people".