A test performance study (TPS) involving 26 European laboratories was conducted to evaluate the robustness and reliability of loop mediated isothermal amplification (LAMP) assays. These assays were for the detection of the quarantine listed species Liriomyza huidobrensis (a leaf mining insect) and Clavibacter michiganensis subsp. sepedonicus (CMS, a bacterial potato pathogen). The L. huidobrensis assay performed well with the main challenge being the interpretation of the results from non-target genera and DNA extraction from small insect parts. Many participants had problems with contamination of the CMS LAMP assay, and a decrease in the limit of detection for the assay was found. Some users found the correct interpretation of LAMP results difficult, and variation was seen upon the use of different amplification platforms. The TPS has highlighted that thorough training prior to implementation of a new diagnostic method would be beneficial, even in the hands of experienced diagnostic laboratories. Useful information has been gathered around the requirements for user instructions/protocols and the formulation of TPS material. Overall the feedback from the participants was positive and LAMP was viewed as a useful new tool, with the speed of testing and simple DNA extraction protocols particularly attractive to laboratories.