  A framework based on a class of abelian gauge symmetries is proposed in which
the masses of only the third generation quarks and leptons arise at the tree
level. The fermions of the first and second families receive their masses
through radiative corrections induced by the new gauge bosons in the loops. It
is shown that the class of abelian symmetries which can viably implement this
mechanism are flavour non-universal in nature. Taking the all-fermion
generalization of the well-known leptonic $L_\mu-L_\tau$ and $L_e - L_\mu$
symmetries, we construct an explicit renormalizable model based on two $U(1)$
which is shown to reproduce the observed fermion mass spectrum of the Standard
Model. The first and second generation fermion masses are loop suppressed while
the hierarchy between these two generations results from a gap between the
masses of two vector bosons of the extended gauge symmetries. Several
phenomenological aspects of the flavourful new physics are discussed and lower
limits on the masses of the vector bosons are derived.
