19 May 1984,
13 members from Navarra were expelled from the party by the PNV executive assembly. The PNV reached an agreement with the Popular Coalition in Navarra to create a centre-right government. However, the party’s Navarros did not share the decision, and the party’s three parliamentarians voted another in the investiture session enabling the PSN presidency, Gabriel Urralburu. They and ten members of Nafarroa Buru Batzar were expelled. This caused a great division within the NIP and was one of the foundational reasons for AD.
Source:
El País (20 May 1984).