Kerala Minister for Water Resources Mathew T Thomas resigned on Monday in accordance with a decision by the national leadership of the Janata Dal-Secular (JD-S).
The party has decided to replace Thomas with veteran K Krishnankutty.
With Thomas submitting his resignation to Chief Minister Pinarayi Vijayan earlier in the day, he became the fourth minister to quit the Vijayan cabinet since it assumed office in 2016.
Thomas addressed the media outside Vijayan's residence and said there was no pre-condition to his quitting.
"There is no question of me moving towards the 'right'. The natural place of the Socialist is always with the Left and there is no question of me moving anywhere else," said Thomas as he was prodded about his next move.
The JD-S is the third largest ally of the CPI-M-led government and has three legislators Thomas, former State Minister CK Nanu and K Krishnankutty.
JD-S national president and former Prime Minister HD Deve Gowda called his three legislators to Bengaluru last week, but Thomas did not turn up and the meeting with the others took place on Friday, when the decision was taken.
Even though Thomas denied that there was an agreement that he would step down after completing half the term of five years, the other faction in the party led by Krishnankutty has always claimed there was one.
Thomas also denied he was in the running for the post of the party president in the state unit, as Krishnankutty would be soon sworn in.
In the past, CPI-M's EP Jayarajan had quit over nepotism allegations, NCP leader AK Saseendran quit over sleaze allegation and Thomas Chandy, who replaced him, quit over land grab allegations.
Earlier in 2018, both Jayarajan and Saseendran had returned to the cabinet after the court cleared them.