The Trinamool Congress confirmed Aleixo Lourenco's resignation in a statement.
A month after switching over to the Trinamool Congress from the Congress and just weeks ahead of the assembly elections, former Goa MLA Aleixo Reginaldo Lourenco on Sunday quit the Mamata Banerjee-led party.
Mr Lourenco was the MLA from Curtorim and was the working president of the Goa Congress when he quit the party and the state assembly in December.
He did not give any reason in the letter that he sent to Ms Banerjee informing her of his decision to leave the Trinamool.
The move instantly prompted an invitation from BJP-turned-Congress leader Micheal Lobo for Mr Lourenco to return to the Congress.
The Trinamool Congress confirmed Mr Lourenco's resignation in a statement.
"AITC has received a letter from Aleixo Reginaldo Lourenco resigning from party's primary membership. We had welcomed him into the party as we have countless others. Now that he wishes to leave, we wish him well," the party's Goa in-charge Mahua Moitra said.
Reports say Mr Lourenco could rejoin the Congress and fight from the Curtorim seat as announced by the party before he quit.
The Congress had not announced an alternative candidate for the Curtorim seat after his departure.
However, it had reacted sharply to Mr Lourenco's resignation, saying people who betray the trust will face the consequences and that voters will teach him a "befitting lesson".
The politician was among various new entrants in the Trinamool ahead of these elections which have seen the party take a more assertive stance facing off with the Congress for the position of the dominant opposition party.
A few months before him, former Goa Chief Minister Luizinho Faleiro had also quit the Congress and joined the Trinamool.
Trinamool chief Mamata Banerjee has made several visits to Goa and addressed public meetings ahead of the elections scheduled for February 14 with counting on March 10.