[4] The longest serving partner in government for Christian Democracy,[5] the PSDI was an important force in Italian politics,[6] before the 1990s decline in votes and members.

[13] When Enrico Ferri founded with Luigi Preti the current European Liberal Social Democracy (SOLE), which was in favour of an alliance with Silvio Berlusconi's centre-right coalition, the choice was stigmatized by the PES and the Socialist International, and an official statement was issued.

The split, led by Giuseppe Saragat and the sons of Giacomo Matteotti, took the name ofscissione di Palazzo Barberini, from the name of a palace in Rome where it took place.

The 1994 Italian general election resulted in an almost overnight decline of the Pentapartito coalition parties and the rise of Silvio Berlusconi-led Forza Italia, which absorbed many PSDI voters.

In January 1995, Gian Franco Schietroma was elected national secretary of the party replacing Enrico Ferri, who wanted to join the centre-right Pole of Freedoms.

The followers of Ferri left and established the European Liberal Social Democracy and joined the centre-right Christian Democratic Centre (CDC).

In that occasion, the party was successful in stealing many votes from the PSI, which was damaged by the split as well as by the alliance with the PCI in the Popular Democratic Front.