Wireless sensor networks have the limitations of energy. An efficient MAC protocol has to be applied to serve the purpose of energy saving and also aiming to make it cost efficient. This paper presents a novel hybrid MAC protocol that uses the information of clusters from routing layer to divide the MAC layer functionality into two types, namely, TDMA based intra-cluster communication and CSMA based inter-cluster communication. A distinctive feature of this approach is its robustness to synchronization errors and the associated power consumptions and delay performances are also computed resulting due to optimized performance of the hybrid mode for cluster organization. Simulation results show that this hybrid MAC layer thus considerably reduces the energy consumption in network nodes thereby increasing the total network lifetime.