  We consider the extended supersymmetric Pati-Salam model which, for mu>0 and
universal boundary conditions, succeeds to yield experimentally acceptable
b-quark masses by moderately violating Yukawa unification. It is known that
this model can lead to new shifted or new smooth hybrid inflation. We show that
a successful two-stage inflationary scenario can be realized within this model
based only on renormalizable superpotential interactions. The cosmological
scales exit the horizon during the first stage of inflation, which is of the
standard hybrid type and takes place along the trivial flat direction with the
inflaton driven by radiative corrections. Spectral indices compatible with the
recent data can be achieved in global supersymmetry or minimal supergravity by
restricting the number of e-foldings of our present horizon during the first
inflationary stage. The additional e-foldings needed for solving the horizon
and flatness problems are naturally provided by a second stage of inflation,
which occurs mainly along the built-in new smooth hybrid inflationary path
appearing right after the destabilization of the trivial flat direction at its
critical point. Monopoles are formed at the end of the first stage of inflation
and are, subsequently, diluted by the second stage of inflation to become
utterly negligible in the present universe for almost all (for all) the allowed
values of the parameters in the case of global supersymmetry (minimal
supergravity).
