"To express our opposition to the AIADMK government, we will vote against the Palaniswami government in the motion of confidence that will be taken up tomorrow," Stalin said.
He blamed the ruling AIADMK for its "failure" on several fronts, including the "deteriorating law and order situation."
TN Congress Committee President Su Thirunavukkarasar said the party would decide its stand on voting based on the advice of the Congress high command.
He denied reports in a section of the media and social media that eight Congress MLAs would vote against the government.
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Earlier, he chaired a meeting of party legislators, led by Congress Legislature Party leader K R Ramasamy and senior functionaries at the Satyamurthi Bhavan.
He said party chief Sonia Gandhi and vice president Rahul Gandhi would be apprised of the views of the state leadership.
On the demand for secret ballot tomorrow, Stalin told reporters, "We are ready to welcome it."
While DMK has a strength of 89, Congress has eight, IUML one in the Assembly and one seat is vacant.
The House has a total strength of 234 members, including that of Speaker.
AIADMK has a total of 134 legislators, including the O Panneerselvam camp followers.