A shell finite element with transverse stress is presented in this paper in order to simulate the forming of thermoplastic composites reinforced with continuous fibres. It is shown by an experimental work that many porosities occurs through the thickness of the composite during the heating and the forming process. Consequently the reconsolidation i.e. the porosity removing by applying a compressive stress through the thickness is a main point of the process. The presented shell finite element keeps the five degrees of freedom of the standard shell elements and adds a sixth one which is the variation in thickness. A locking phenomenon is avoided by uncoupling bending and pinching in the material law. A set of classical validation tests will prove the efficiency of this approach. Finally a forming process is simulated. It shows that the computed transverse stresses are in good agreement with porosity removing in the experiments.