Nine Congress legislators, owing allegiance to K Karunakaran, on Tuesday resigned from the Kerala assembly and joined the veteran leader's National Congress (Indira) party.
The MLAs handed over the resignation letters to Speaker Therambil Ramakrishnan.
The MLAs who resigned are P Sankaran, M P Gangadharan, M A Chandrasekharan, N D Appachan, Maleth Sarala Devi, Radha Raghavan, T V Chandramohan, Sobhana George and D Sugathan.
The speaker has accepted the resignations with immediate effect.
A decision to this effect was taken by the MLAs on Monday after a meeting with Karunakaran and NCI president K Muraleedharan.
The development poses no threat to the stability of the Ommen Chandy government in the state.