Thakor, who represented the last Lok Sabha from Patan in north Gujarat, sent his resignation to the party high command to exercise pressure on it as he was angling for the chairmanship of the campaign committee for the 2017 assembly elections.
The sources said the party had finalized Siddharth Patel, senior leader and son of late party veteran Chimanbhai Patel, to head the campaign committee as he hails from the Patel community and is non-controversial.
Thakor has also resigned from all other party posts.
He was not available for comment while the Congress did not provide any official confirmation of his resignation.
The exact reason for his quitting is not officially known though it is an open secret that Thakor did not see eye to eye with state Congress President Bharatsinh Solanki.
Congress spokesperson Manish Doshi said: "The party has not received any resignation letter from him."
Doshi said Thakor did not hold any party position currently while "he was just a former MP and MLA".
However, a senior leader said Thakor's action was not a good omen.
With the Dalits and Muslims already believed to be with the Congress, it was vital that the OBCs must remain with the party, the leader said.
