A variable displacement pump for fluids, comprising: - a pump body having a cavity; - a regulation ring or stator mounted within said cavity and arranged to move, in response to operating conditions of the pump, between two extreme positions corresponding to a maximum displacement and a minimum displacement, respectively, of the pump; - a rotor accomodated in a chamber of the regulation ring; and - a spring opposing the movement of the regulation ring; wherein the regulation ring has at least a pair of actuation stages (19, 20) having mutually differing surfaces, a first of said actuation stages being permanently exposed to pressure conditions of the pumped fluid and being arranged to make the regulation ring move against the action of the spring, and a second of said actuation stages being arranged to act concordantly with the spring in a manner controlled by an electrically-controlled valve; wherein: - a spool valve is connected between the second stage and the electrically-controlled valve and is arranged to modulate a regulation pressure acting on the second stage depending on a control signal supplied by the electrically-controlled valve and on the pressure conditions of the pumped fluid, characterised in that the pump is a pump for a lubrication circuit of an engine, in that said movement of the regulation ring is a rotation about a rotation axis internal to the regulation ring, in that the spring is a helical spring having a longitudinal axis which does not cross the rotation axis of the regulation ring, is located in a seat formed in the pump body and has end loops (23A, 23B) which abut against a flat end surface of the seat and on a flat portion of an external surface of regulation ring, and in that said flat end surface and said flat portion have formed thereon centring projections or recesses (26, 27) engaging end loops (23A, 23B) of the spring and configured for maintaining said end loops (23A, 23B) univocally positioned and preventing the spring from sliding over said flat end surface and flat end portion, said centring projections or recesses (26, 27) have no guiding function so that the spring has an intermediate portion freely deformable during the rotation of the regulation ring. - a pump body having a cavity; - a regulation ring or stator mounted within said cavity and arranged to move, in response to operating conditions of the pump, between two extreme positions corresponding to a maximum displacement and a minimum displacement, respectively, of the pump; - a rotor accomodated in a chamber of the regulation ring; and - a spring opposing the movement of the regulation ring; wherein: - a spool valve is connected between the second stage and the electrically-controlled valve and is arranged to modulate a regulation pressure acting on the second stage depending on a control signal supplied by the electrically-controlled valve and on the pressure conditions of the pumped fluid, - a spool valve is connected between the second stage and the electrically-controlled valve and is arranged to modulate a regulation pressure acting on the second stage depending on a control signal supplied by the electrically-controlled valve and on the pressure conditions of the pumped fluid, characterised in that the pump is a pump for a lubrication circuit of an engine, in that said movement of the regulation ring is a rotation about a rotation axis internal to the regulation ring, in that the spring is a helical spring having a longitudinal axis which does not cross the rotation axis of the regulation ring, is located in a seat formed in the pump body and has end loops (23A, 23B) which abut against a flat end surface of the seat and on a flat portion of an external surface of regulation ring, and in that said flat end surface and said flat portion have formed thereon centring projections or recesses (26, 27) engaging end loops (23A, 23B) of the spring and configured for maintaining said end loops (23A, 23B) univocally positioned and preventing the spring from sliding over said flat end surface and flat end portion, said centring projections or recesses (26, 27) have no guiding function so that the spring has an intermediate portion freely deformable during the rotation of the regulation ring.