A motor control circuit for an electric motor of an electric power assisted steering system of the kind in which a measurement of torque carried by a part of the steering system is used to produce a torque demand signal indicative of a torque to be applied to the steering system by the motor, the motor control circuit comprising: a switching circuit comprising a plurality of electrical switches (16, 18), a current demand signal generator which converts the torque demand signal into a current demands signal; a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches (16, 18) that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases; in which the drive circuit for the switches (16, 18) is arranged to apply the voltage across the single combined phases so that the polarity of the voltage is reversed each time the motor has rotated through 180 degrees and in which the start and end of the 180 degree rotation is aligned with the position of the faulted phase; and characterized in that the switch means is driven in a first mode to apply the voltage demanded by the controller across the single combined phase by clamping a first end of the combined phase to the positive supply and applying a PWM signal to the second end of the combined phase over one half of an electrical rotation of the motor rotor, and during the other half of the electrical rotation of the rotor the switch means are driven in a second mode by clamping the second end to ground and applying a PWM signal to the first end, the changeover between the two modes corresponding to the position of the failed open circuit phase. a switching circuit comprising a plurality of electrical switches (16, 18), a current demand signal generator which converts the torque demand signal into a current demands signal; a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches (16, 18) that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases; in which the drive circuit for the switches (16, 18) is arranged to apply the voltage across the single combined phases so that the polarity of the voltage is reversed each time the motor has rotated through 180 degrees and in which the start and end of the 180 degree rotation is aligned with the position of the faulted phase; and characterized in that the switch means is driven in a first mode to apply the voltage demanded by the controller across the single combined phase by clamping a first end of the combined phase to the positive supply and applying a PWM signal to the second end of the combined phase over one half of an electrical rotation of the motor rotor, and during the other half of the electrical rotation of the rotor the switch means are driven in a second mode by clamping the second end to ground and applying a PWM signal to the first end, the changeover between the two modes corresponding to the position of the failed open circuit phase.