The invention relates to a controller (140) for a parallel hybrid electric vehicle having a powertrain comprising an engine (121), electric propulsion means (123B; 123C) powered by energy storage means (150), and electric generator means (123B; 123C) operable to be driven by the engine (121) to recharge the energy storage means. The controller (140) is operable to: receive one or more signals indicative of one or more operating modes in which the vehicle is to be operated at a given moment in time, the one or more operating modes being selected from a plurality of operating modes; receive a signal indicative of demanded powertrain drive torque; and cause the engine (121) and electric propulsion means (123B; 123C) to deliver drive torque to one or more wheels (111; 112; 113; 114) to drive the vehicle in dependence on the signal indicative of demanded powertrain drive torque, the controller (140) being operable to cause the powertrain to operate in a parallel powertrain mode in which the controller is operable to cause the electric propulsion means (123B;123C) to apply drive torque to the one or more wheels in addition to the engine (121), the amount of torque delivered by the electric propulsion means being determined by the controller (140) at least in part in dependence on the signal indicative of demanded powertrain drive torque and the one or more signals indicative of the one or more operating modes in which the vehicle is to be operated. The invention also relates to a corresponding method.