The Spanish Constitution has been reformed once (Article 13.2, Title I) to extend to citizens of the European Union the right to active and passive suffrage (both voting rights and eligibility as candidates) in local elections.

The socialist government of José Luis Rodríguez Zapatero has announced its intention to undertake a major reform of the constitution during its tenure. The proposed modifications would include

1. succession in the monarchy on the basis of age only, and not gender, thus abandoning the traditional Castilian rules set in the Siete Partidas . While the rights of the current heir apparent Felipe, Prince of Asturias, are to be maintained, the goal is to reform before his eventual children are born.
2. an overhaul of the Spanish Senate transforming it into a chamber of territorial representation
3. officially incorporating the European Constitution (should one be approved)
4. modifying the organisation of the autonomous communities

The proposal has been met with scepticism from some quarters (notably the main opposition party PP) because some of these reforms affect protected sections of the constitution, undertaking their reform would require an entirely new constitution (see below). Furthermore, even an amendment of a non-protected part of the Constitution would require PP agreement, because it would require the support of 3/5 of each House: that's 210 votes in the Congress of Deputies and 156 in the Senate, while the maximum majority without the PP is 202 votes in the Congress of Deputies and 133 in the Senate.

Protected provisions

The Constitution itself determines in Title X that a new constitution must be written, should there be the need to reform the Preliminary Title; Title I, Section I, Chapter II; or Title II. These "special" sections indicate what the drafters of the constitution considered fundamental about the regime they were establishing: that the "fundamental rights and public liberties" cannot be changed without regime change; and that Spain is a constitutional monarchy. From a logical point of view, since Title X is does not protect itself, it would be possible to first reform Title X and then change the previously protected articles.

The Ibarretxe Plan

The plan conducted by the Basque president Juan José Ibarretxe (known as Ibarretxe Plan ) to reform the status of the Basque Country in the Spanish state has been rejected by the Spanish Cortes, on the grounds (among others) that it amounts to an implicit reform of the Constitution.