  We forecast the future constraints on scale-dependent parametrizations of
galaxy bias and their impact on the estimate of cosmological parameters from
the power spectrum of galaxies measured in a spectroscopic redshift survey. For
the latter we assume a wide survey at relatively large redshifts, similar to
the planned Euclid survey, as baseline for future experiments. To assess the
impact of the bias we perform a Fisher matrix analysis and we adopt two
different parametrizations of scale-dependent bias. The fiducial models for
galaxy bias are calibrated using a mock catalogs of H$\alpha$ emitting galaxies
mimicking the expected properties of the objects that will be targeted by the
Euclid survey.
  In our analysis we have obtained two main results. First of all, allowing for
a scale-dependent bias does not significantly increase the errors on the other
cosmological parameters apart from the rms amplitude of density fluctuations,
$\sigma_{8}$, and the growth index $\gamma$, whose uncertainties increase by a
factor up to two, depending on the bias model adopted. Second, we find that the
accuracy in the linear bias parameter $b_{0}$ can be estimated to within 1-2\%
at various redshifts regardless of the fiducial model. The non-linear bias
parameters have significantly large errors that depend on the model adopted.
Despite of this, in the more realistic scenarios departures from the simple
linear bias prescription can be detected with a $\sim2\,\sigma$ significance at
each redshift explored.
  Finally, we use the Fisher Matrix formalism to assess the impact of assuming
an incorrect bias model and found that the systematic errors induced on the
cosmological parameters are similar or even larger than the statistical ones.
