  We address the question of how to represent an interacting action for the
tower of conformal higher spin fields in a form covariant with respect to a
background metric. We use a background metric to define a star product which
plays a central role in the definition of the corresponding gauge
transformations. By an analogy with the kinetic term in the 4-derivative Weyl
gravity action expanded near an on-shell background one expects that the
kinetic term in such an action should be gauge-invariant in a Bach-flat metric.
We demonstrate this fact to first order in expansion in powers of the curvature
of the background metric. This generalizes the result of arXiv:1404.7452 for
spin 3 case to all conformal higher spins. We also comment on a possibility of
extending this claim to terms quadratic in the curvature and discuss the
appearance of background-dependent mixing terms in the quadratic part of the
conformal higher spin action.
