The excitation of cosmological perturbations in an anisotropic cosmological model, in the presence of a homogeneous magnetic field has been studied, using the ideal magnetohydrodynamic (MHD) equations. We have shown that fast-magnetosonic modes, propagating normal to the magnetic field are excited. At late times, the magnetic induction contrast $(\dl B / B)$ grows according to a power-law temporal dependence, resulting in the amplification of the ambient magnetic field. This process can be particularly favored by condensations formed within the plasma fluid.