The Permanent Commission created at the assembly in Iruñea called all the municipal representatives in the Basque Country to a meeting at the Euskalduna Palace in Bilbo on 18 September 1999 in order to create a Basque national institution.

1,788 elected representatives from 354 municipalities in all the provinces in the Basque Country attended the meeting. In fact, this assembly was better attended than the previous one in Iruñea, as can be seen by the long list of people there: highest level representatives of the political parties and social agents in the Basque Country, media from all over the world, international guests…
The Permanent Commission created in Iruñea put four proposals to the Assembly:

1. The creation of a national institution based on municipalities.
2. Giving a name to the institution.
3. The creation of five workgroups to carry out the work of the institution.
4. Appointing a new Executive Committee.

All four proposals were passed and as a consequence UDALBILTZA, Assembly of Basque Elected Municipal Representatives, was born.
The foundational political declaration included, amongst other points, the aims of Udalbiltza:

1. To demand recognition for the Basque Country as a nation.
2. To contribute to build a political structure for the Basque Country.
3. To promote nation-building in the Basque Country.
4. To contribute to strengthen ties among the town halls from all the provinces in the Basque Country by channelling joint action by municipal representatives in various fields.
5. To foster recognition of the Basque Country as a nation in its own rights before the international community.

Finally, in order to lead and articulate the work of Udalbiltza, an Executive Committee made up of 15 mayors and councillors, which reflected the political and territorial diversity of that general assembly, was appointed.