The present invention concerns an elongated elastic support element 16 for a wiper blade 10 intended to be inserted in a support 14 for a wiper blade 10, the elongated elastic support element 16 being formed integrally between two longitudinal ends 16a and through which passes a median longitudinal plane P1, the elongated elastic support element comprising locking means 50 each intended to cooperate with a complementary locking member 56 carried by the wiper blade 10, and of which at least one locking means 50 is arranged at each longitudinal end 16a of the elongated elastic support element 16, characterized in that the locking means 50 comprise a single locking notch 50 per longitudinal end 16a, a first locking notch 50b extending from one side of the median longitudinal plane P1 and a second locking notch 50c extending from the other side of the median longitudinal plane P1. The invention also concerns a wiper blade 10 and a windscreen wiper 1 of a motor vehicle comprising said blade.