This technical report describes the composite indicator developed by JRC to rank plant pests based on their potential economic, social and environmental impact in the EU. This indicator can then be used to inform policy makers implementing the Plant Health Regulation with regards to identification of priority pests. It presents the theoretical framework for the construction of the composite impact indicator for prioritization of pests (I2P2), and defines and discusses the individual indicators which compose the I2P2 together with the data sources used to calculate them using T. indica as an example. Last the I2P2 is applied to a set of 28 Union quarantine pests to show its performance. Using the data of these 28 pests, consistency and robustness checks are applied to test the internal validity of the indicator.