Testing the Lorentz structure of the charged weak current in tau-decays

We review the current experimental situation on the determination of the Lorentz structure of the charged weak current in tau decays. We propose a method to extent these studies to decays of tau leptons to righthanded daughter leptons which are forbidden in the standard model. We reanalyse the available data in the framework of specific models and derive Limits on the mass of charged Higgs bosons of m(H+/-) > 1.5 tan beta GeV at 90 % c.l. and on righthanded W-bosons of m(W-2) > 230 GeV at 90 % c.l,, valid if the righthanded neutrinos associated with it are light compared to the tau.