The photon asymmetry in the reaction p(\vec {\gamma },\pi ⁰)p has been measured with the photon spectrometer TAPS using linearly polarized photons from the tagged-photon facility at the Mainz Microtron MAMI close to the pion threshold and in the  \Delta (1232)-resonance region. The total and differential cross sections were also measured simultaneously with the photon asymmetry. This allowed determination of the S-wave and all three P-wave amplitudes. The results in the threshold region are compared to the predictions of ChPT. With the photon spectrometer TAPS the full polar angular range of the pion could be covered and from the new results in the \Delta (1232) region a E2/M1-ratio of -(2.4 \pm 0.16_stat. \pm 0.24_sys.) \% is extracted.

PACS numbers: 13.60.Le, 14.20.Gk, 13.60.Rj