  We study the non-linear background field redefinitions arising at the quantum
level in a spontaneously broken effective gauge field theory. The non-linear
field redefinitions are crucial for the symmetric (i.e. fulfilling all the
relevant functional identities of the theory) renormalization of
gauge-invariant operators. In a general $R_\xi$-gauge the classical
background-quantum splitting is also non-linearly deformed by radiative
corrections. In the Landau gauge these deformations vanish to all orders in the
loop expansion.
