The authors consider \(h\)-adaptive finite elements solutions of problems in non-associated plasticity. Here, more than in associated plasticity, strong localisations may arise – sometimes giving rise to the so-called mesh-dependent solutions, i.e. no real convergence can be achieved as the problem is not well formulated. The authors therefore consider the formulation in the realm of Cosserat continua where each point has not only three degrees of freedom of normal Cauchy continuum, but six degrees of freedom of rigid body. This approach effectively introduces a length scale into the constitutive equations. Comparative computations show the advantage of the new formulation.