  Poincar\'e gauge theories provide an approach to gravity based on the gauging
of the Poincar\'e group, whose homogeneous part generates curvature while the
translational sector gives rise to torsion. In this note we revisit the
stability of the widely studied quadratic theories within this framework. We
analyse the presence of ghosts without fixing any background by obtaining the
relevant interactions in an exact post-Riemannian expansion. We find that the
axial sector of the theory exhibits ghostly couplings to the graviton sector
that render the theory unstable. Remarkably, imposing the absence of these
pathological couplings results in a theory where either the axial sector or the
torsion trace becomes a ghost. We conclude that imposing ghost-freedom
generically leads to a non-dynamical torsion. We analyse however two special
choices of parameters that allow a dynamical scalar in the torsion and obtain
the corresponding effective action where the dynamics of the scalar is
apparent. These special cases are shown to be equivalent to a generalised
Brans-Dicke theory and a Holst Lagrangian with a dynamical Barbero-Immirzi
pseudoscalar field respectively. The two sectors can co-exist giving a
bi-scalar theory. Finally, we discuss how the ghost nature of the vector sector
can be avoided by including additional dimension four operators.
