  Within the standard V - A theory of weak interactions, Quantum
Electrodynamics (QED) and the linear sigma-model (LsM) of strong low-energy
hadronic interactions we analyse gauge and infrared properties of hadronic
structure of the neutron and proton in the neutron beta decay to leading order
in the large nucleon mass expansion. We show that the complete set of Feynman
diagrams describing radiative corrections of order O(\alpha/\pi), induced by
hadronic structure of the nucleon, to the rate of the neutron beta decay is
gauge non-invariant and unrenormalisable. We show that a gauge non-invariant
contribution does not depend on the electron energy in agreement with Sirlin's
analysis of contributions of strong low-energy interactions (Phys. Rev. 164,
1767 (1967)). We show that infrared divergent and dependent on the electron
energy contributions from the neutron radiative beta decay and neutron beta
decay, caused by hadronic structure of the nucleon, are cancelled in the
neutron lifetime. Nevertheless, we find that divergent contributions of virtual
photon exchanges to the neutron lifetime, induced by hadronic structure of the
nucleon, are unrenormalisable even formally. Such an unrenormalizability can be
explained by the fact that the effective V - A vertex of hadron-lepton
current-current interactions is not a vertex of the combined quantum field
theory including QED and LsM, which are renormalizable theories.
