  Sutherland's theorem dictates that the contribution of the electromagnetic
interaction to the decay process (\eta\rightarrow 3\pi^{0}) is neglected with
respect to the one coming from the difference between the up and down quark
masses. In the framework of chiral perturbation theory including virtual
photons, we calculated the main diagram concerning the exchange of a virtual
photon between two intermediate charged pions. The correction induced by this
diagram on the slope parameter amounts to (17%) of the correction induced by
the pure strong interaction at one-loop level. If this result is maintained
when considering all the diagrams at the chiral order we are working, we can
say without any doubt that Sutherland's theorem is strongly violated. As a
direct consequence, any determination of light quark masses from the present
decay \textit{should} take into account the electromagnetic interaction.
