  We calculate the power spectra of primordial curvature and isocurvature
perturbations from a general two field inflation model at next-to-leading order
correction in a slow-roll expansion. In particular we calculate the spectral
indices to second order in slow-roll parameters. We show that the
cross-correlation of the curvature and isocurvature perturbations at the time
of Hubble-exit during inflation is non-zero at first-order in slow-roll
parameters. We apply our results to different classes of inflation, including
inflaton and curvaton scenarios. The spectrum of primordial gravitational
waves, curvature and isocurvature perturbations obey generalised consistency
relations in two-field inflation models. We give the first two consistency
relations in an infinite hierarchy.
