  The dependence of K_{S,L}->\pi^{+}\pi^{-}\gamma decay probabilities on photon
polarization is calculated. The phases of terms of amplitude that arise from
the pion-pion interaction are obtained by using a simple realistic model of
pion-pion interaction via virtual \rho-meson, instead of the ChPT. The results
are compared with those of other authors and the origin of slight discrepancies
is explained. It is shown that the standard ChPT approach for K_{S,L}->
\pi^{+}\pi^{-}\gamma decays cannot reproduce the contribution of the \rho-meson
to the P-wave \pi\pi interaction. The departure of the photon spectrum from
pure bremsstrahlung due to the pion loop contribution to the direct emission
amplitude is calculated. It is shown that the interference between the terms of
amplitude with different CP-parity appears only when the photon is polarized
(linearly or circularly). Instead of measuring the linear polarization, the
angular correlation between the \pi^{+}\pi^{-} and e^{+}e^{-} planes in
K_{S,L}->\pi^{+}\pi^{-}e^{+}e^{-} decay can be studied.
