The multiparty nature of multicast applications presents new challenges for Mobile IP users. Unfortunately, when a multicast receiver is mobile, it will experience additional delay in receiving multicast packets due to handover delay, join latency, and increased propagation delay to the new location. In this paper we propose a new solution to avoid the multicast triangle routing problem inside the home network when the Mobile IP bidirectional tunnelling approach is used. Our solution is based on the use of a new architectural entity called "Multicast Router Proxy". The proxy is used to redirect multicast traffic to the mobile receiver and avoid redundant multicast traffic passage to the Home Agent. In addition, we enhance the functionalities of the Home Agent to efficiently manage the multicast membership information for mobile receivers that are located outside the home network.