AIADMK's leader, Jayalalitha Jayaram, is a controversial former actress who has threatened such action before only to withdraw after winning concessions.

ECONOMIST: India

The issue of Sri Lankan Tamils was also raised in parliament by MPs from the DMK and AIADMK, another regional party from Tamil Nadu.

BBC: India DMK party ministers leave government

But neither of this state's most powerful politicians - the former film script writer Karunanidhi of the DMK, and the former actress Jayalalithaa of the AIADMK - is actually standing in this election.

BBC: Tamil Nadu: India's kingmaker state