Kerala Chief Minister Oommen Chandy on Sunday threatened to sue former chief minister V.S. Achutanandan if he did not stop telling "lies".Chandy said in a statement that the Marxist leader had said in a campaign speech that there were 136 cases registered against all except one minister in the state cabinet."Achutanandan says there are 31 cases registered against me. He should immediately tell me which are these cases. If he does not, I will be forced to take legal steps against him for this baseless slander," said Chandy."A mere complaint or a petition does not become a case. The first step in a case is registering an FIR. Achuthanandan should produce one FIR," the chief minister added."The only FIR that's there is against former finance minister K.M. Mani and the state vigilance has submitted it to the court exonerating him and is right now in front of the vigilance court."He (Marxist leader) will soon have to withdraw this baseless statement and he is doing all this because he has got nothing to say against us and hence he is bluffing," Chandy added.Chandy and Achutanandan are the star campaigners for their respective fronts: the ruling United Democratic Front and the Left Democratic Front.