In this paper, we present REMI, a reliable and secure multicast routing protocol for IoT networks. The main aim of REMI is to enable efficient communication in low-power and lossy networks such as IoT, by ensuring that a message will be received by all its intended destinations, irrespective of the network size and the presence of misbehaving nodes. REMI uses a cluster-based routing approach that triggers a faster multicast dissemination of messages within the network. We implemented REMI with Contiki, a multitasking operating system which is widely adopted by industry for deploying energy-constrained and memory-efficient wireless networks. To assess the effectiveness and efficiency of REMI, we run a thorough set of simulations. Our results show the effectiveness of our protocol over state-of-art protocols in terms of network throughput, propagation delay, and scalability at the cost of minimal overheads in terms of energy consumption and memory utilization.