If monetary union is not embedded from the outset in a largely homogeneous and political union which is constituted along the lines of national government, but is founded instead on the basis of different nation states, that supranational monetary policy can only be largely unpolitical, meaning disengaged from the political influence of nation states which goes beyond the legal mandate to safeguard the stability of the currency.
This is particularly valid as long as there is no all-encompassing decision-making process at the European level -- and that will probably not exist in Europe for a long time to come.