In this paper, a new static voltage stability index is proposed for identifying the line or its corresponding bus on the verge of voltage collapse of distribution networks. The index is developed by using the distribution line receiving end bus voltage formulation, and its adequacy is evaluated on a modern distribution test system which has voltage controlled bus (PV-bus). From analyses, it is observed that the proposed stability index correctly predict the critical line and its corresponding bus as well, and can provide useful information for the most sensitive line at any operating point of distribution networks. On the other hand, most of the existing voltage stability indices do not correctly estimate the critical bus or its corresponding line for this particular distribution network. In addition, the estimation about the most critical bus or line by using these stability indices for the any operation point of radial systems may cause utilities a wrong conclusion on the critical bus or its corresponding line because they would be inadequate for assessing the most sensitive bus or line in such distribution networks. © 2010 Praise Worthy Prize S.r.l. - All rights reserved.