We show how a novel fine-tuning problem present in the Standard Model can be
solved through the introduction of a single flavour symmetry G, together with
three Q=−1/3 quarks, three Q=2/3 quarks, as well as a complex singlet
scalar. The symmetry G is extended to the additional fields and it is an exact
symmetry of the Lagrangian, only spontaneously broken by the vacuum. Specific
examples are given and a phenomenological analysis of the main features of the
model is presented. It is shown that even for vector-like quarks with masses
accessible at the LHC, one can have realistic quark masses and mixing, while
respecting the strict constraints on process arising from flavour changing
neutral currents (FCNC). The vector-like quark decay channels are also
described.Comment: 25 pages, no figure
