"I will submit my resignation as the GST panel chief tomorrow," he told PTI.
"I will send my resignation to the Centre tomorrow at about 10.00 A.M.," Modi said.
Modi's announcement came after Bihar chief minister Nitish Kumar removed 11 BJP ministers, including Modi, from his council of ministers following the parting of ways with NDA.
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The former deputy chief minister had also held the finance portfolio in the NDA government in Bihar.
As the GST panel chief, Modi would hold parleys with state finance ministers for implementation of the uniform tax regime.
He had assumed the post after the then GST panel chairman Asim Dasgupta's CPI(M)-led Left Front bowed out of power in West Bengal.