  We consider the general orthogonal metric separable in space and time
variables in comoving coordinates. We then characterise perfect fluid models
admitted by such a metric. It turns out that the homogeneous models can only be
either FLRW or Bianchi I while the inhomogeneous ones can only admit $G_2 $
(two mutually as well as hypersurface orthogonal spacelike Killing vectors)
isometry. The latter can possess singularities of various kinds or none. The
non-singular family is however unique and cylindrically symmetric.
