A good deal of research and development has been carried out in architecture and protocol design, energy saving and location, but only a few studies have been done on network performance in WSN (Quality of Service-QoS). The commonly accepted QoS metrics include bandwidth, delay, delay jitter and reliability. Whereas the majority of developed applications for WSNs are event-critical applications, achieving reliable data transfer as the main factor of dependability and quality of service seems vital. In many applications, the reliability level required by the data packets is different. Also, there are some applications in which the significance of the data obtained from the sensor nodes, depends on the majority of the reports denoting occurrence of specific events in some parts of the environment. In this paper, we focus on building a routing protocol called MBRR which routes packets towards the destination node in a highly reliable manner by classifying data into differentiated classes. Moreover, MBRR employs a new adaptive policy called majority based re-routing policy in order to route the packets with instantaneously change in number implying occurrence of special events via more reliable paths.