Generic irreducibility of parabolic induction for real reductive groups

Let $G$ be a real reductive linear group in the Harish-Chandra class. Suppose that $P$ is a parabolic subgroup of $G$ with Langlands decomposition $P=MAN$. Let $\pi$ be an irreducible representation of the Levi factor $L=MA$. We give sufficient conditions on the infinitesimal character of $\pi$ for the induced representation $i_P^G(\pi )$ to be irreducible. In particular, we prove that if ${\pi }_M$ is an irreducible representation of $M$, then for a generic character ${\chi }_{\nu }$ of $A$, the induced representation $i_P^G({\pi }_M⊠{\chi }_{\nu })$ is irreducible. Here the parameter $\nu$ is in ${\mathfrak{a}}^{\ast }=(\mathrm{L}\mathrm{i}\mathrm{e}(A){\otimes }_{\mathbb{R}}\mathbb{C}{)}^{\ast }$ and generic means outside a countable, locally finite union of hyperplanes which depends only on the infinitesimal character of $\pi$. Notice that there is no other assumption on $\pi$ or ${\pi }_M$ than being irreducible, so the result is not limited to generalised principal series or standard representations, for which the result is already well known.