  We examine the generation of primordial perturbations during an inflationary
epoch in generalised theories of gravity when the equations of motion are
derived using the Palatini variational principle. Both f(R) and Scalar-Tensor
theories are considered and we compare our results with those obtained under
the conventional metric formalism. Non-linear generalisations of the action
lead to different theories under the two variational choices and we obtain
distinct results for scalar and tensor spectral indices and their ratio. We
find the following general result; inflation driven solely by f(R)
modifications alone do not result in suitable curvature perturbations whilst
Scalar-Tensor theories generate nearly scalar invariant curvature perturbations
but no tensor modes.
