Navarrese People's Union
30 April 1988, was another important date in the trajectory of the PRC, due to its participation as an observer in a work group of regionalist parties in Valencia. The group planned a joint project and to present a united candidacy to the European elections of the following year. This work group included Navarrese People's Union, Aragonese Party, Valencian Union, Progressive Riojan Party, Majorcan Union, United Extremadura and United City of Melilla, in addition to the Regionalist Party of Cantabria, which was integrated, in June, as a member of the platform and a year later stood for the elections to European Parliament, comprising the candidacy of the Federation of Regionalist Parties (FPR). Since then, relationships have been maintained between the different regionalist parties that exist in Spain.