  We present a multifrequency approach which optimizes the constraints on
cosmological parameters with respect to extragalactic sources and secondary
anisotropies contamination on small scales. We model with a minimal number of
parameters the expected dominant contaminations in intensity, such as
unresolved point sources and the thermal Sunyaev-Zeldovich effect. The model
for unresolved point sources, either Poisson distributed or clustered, uses
data from Planck early results. The overall amplitude of these contributions
are included in a Markov Chain Monte Carlo analysis for the estimate of
cosmological parameters. We show that our method is robust: as long as the main
contaminants are taken into account the constraints on the cosmological
parameters are unbiased regardless of the realistic uncertainties on the
contaminants. We show also that the two parameters modelling unresolved points
sources are not prior dominated.
