  The problem of corrections to Einstein's equations arising from averaging of
inhomogeneities ("backreaction") in the cosmological context, has gained
considerable attention recently. We present results of analysing cosmological
perturbation theory in the framework of Zalaletdinov's fully covariant
Macroscopic Gravity. We show that this framework can be adapted to the setting
of cosmological perturbations in a manner which is free from gauge related
ambiguities. We derive expressions for the backreaction which can be readily
applied in \emph{any} situation (not necessarily restricted to the linear
perturbations considered here) where the \emph{metric} can be brought to the
perturbed FLRW form. In particular these expressions can be employed in toy
models studying nonlinear structure formation, and possibly also in N-body
simulations. Additionally, we present results of example calculations which
show that the backreaction remains negligible well into the matter dominated
era.
