Addressing reporters here, Thangkabalu said he will send his resignation letter to Congress President Sonia Gandhi soon and will abide by the party high command's decision on the matter.
He, however, added that no party should be ''singled out'' for the DMK-led front's rout in the polls by the AIADMK combine, and said he accepted the people's verdict.
The Congress had at the end of tough negotiations with regional alliance leader DMK secured 63 seats but was overwhelmed by the AIADMK juggernaut, managing to bag only five constituencies.
Thangkabalu, facing flak from various factions in the party for the choice of some candidates, himself had lost to AIADMK's R Rajalakshmi in Mylapore.
Though his wife Jayanthy was initially nominated as Congress candidate for the constituency in Chennai, her papers were rejected and he became the nominee by virtue of being the dummy candidate.
Thangkabalu, a former MP, had been facing a tough time from the party cadre, especially after the candidates were announced for the 63 seats.
He had to face the wrath of supporters of some leaders who, denied tickets, went even to the extent of damaging property at TNCC headquarters, Satyamurthy Bhavan.
The AIADMK-led alliance had won 203 seats while the DMK-combine 31.The Jayalalithaa-led AIADMK secured an absolute majority of its own in the 234-member assembly, bagging 150 seats of the 160 it contested.