The present invention describes a synergistic composition comprising of one or more statins, or one or more dipeptidyl peptidase IV (DPP IV) inhibitor or one or more biguanide antihyperglycaemic agent and a PPAR agonist of formula (Ia) for the treatment of diabetes, especially non-insulin dependent diabetes (NIDDM) or Type 2 diabetes and conditions associated with diabetes mellitus and to compositions suitable for use in such method. The invention also describes the preparation of such compositions. The present invention also relates to certain novel salts of the PPAR agonist of formula (I), processes for the preparation of these novel salts and use thereof.