This paper investigates the stability of the Generalised-α time integration method (the CH method) for a fully coupled solid-pore fluid formulation. Theoretical stability conditions are derived, which are shown to simplify to the existing ones of the CH method for the one–phase formulation when the solid-fluid coupling is ignored. Finite Element (FE) analyses considering a range of loading conditions are conducted to validate the analytically derived stability condition, showing that the numerical results are in agreement with the theoretical investigation. The CH method is a generalisation of a number of other tine integration schemes and hence the derived stability conditions are relevant for most of the commonly utilised time integration methods for fully coupled two-phase formulation.