Weak Corrections to Three - Jet Production in Electron - Positron Annihilations ∗

We report on the calculation of the factorisable one-loop weak-interaction corrections to the initial and final states for three-jet observables in electron-positron annihilations. We show that whereas such corrections are negligibly small at LEP energies they are significantly enhanced at a future Linear Collider, where we argue that they may be similar in size to the two-loop QCD effects. The calculation has been performed using helicity amplitudes so that it can be applied to the case of polarised beams. The effects of beam polarisation can be extracted from an analysis of the angular distributions of the jets relative to the incident electron/positron directions.