'None knows anything about this agreement and none has been taken into confidence,' said Ratnakaran.
Communist Party of India-Marxist (CPI-M) state secretary Pinarayi Vijayan said Kerala has been 'cheated' by the central government.
There would be widespread protests against the FTA, he added.
Earlier in the day, Achuthanandan said in Kozhikode that the central government ignored Kerala's fears over the FTA.
'The decision by the centre to go ahead with it, without looking into the fears of Kerala, is not right,' he told reporters.
Achuthanandan met Prime Minister Manmohan Singh in New Delhi Aug 3 and apprised him of the apprehensions of the state over the agreement.
During the meeting, the prime minister assured him that the 'interests of Kerala farmers will be taken care of' and a copy of the text of the FTA would be given to the state.
However, Achuthanandan claimed none of the promises has been kept.
'Manmohan Singh agreed to give us a copy of the text of the FTA. But we haven't received it yet,' he said.