  The widths of the decays $\rho^{-}\to\eta\pi^{-}$ and
$\tau^{-}\to\eta(\eta')\pi^{-}\nu$ are calculated in the framework of the NJL
model. It is shown that these decays are defined by the $u$ and $d$ quark mass
difference. It leads to the suppression of these decays in comparison with the
main decay modes. In the process $\rho^{-}\to\eta\pi^{-}$ the intermediate
scalar $a_0^{-}$ state is taken into account. For the $\tau$ decays the
intermediate states with $a_0^{-}$, $\rho^{-}(770)$ and $\rho^{-}(1450)$ mesons
are used. Our estimates are compared with the results obtained in other works.
