Results. We found the discs to be formed by conserving the specific angular momentum in accordance with the classical disc formation model. The specific angular momentum of the stellar central spheroid correlates with the dark matter halo angular momentum and determines a power law. Our results suggest that gas accretion to rebuild the disc component is a necessary but not sufficient ingredient for a disc-dominated galaxy in a hierarchical clustering scenario. The survival of the discs is tightly linked to their subsequent history of accretion, as previously reported. Minor mergers play an important role. It is more likely that they will destroy the disc and feed the central spheroid if their angular momentum is misaligned with respect to that of the main galaxy. Conversely, if they are aligned, they can contribute to the disc formation.