Adjustable clamp for securing shuttering panels, the adjustable clamp comprising two substantially L-shaped members (1, 2) articulated on an intermediate support on which rest profiles sections (28, 29) of frames of the panels to be clamped, the L-shaped members (1,2) further comprising a central pin for articulation of the L-shaped members (1,2), a first set of pins (13,13') for the first L-shaped member and a second set of pins (14,14') for the second L-shaped member, whereby: the intermediate support comprises: - an elongated hole perpendicular to a longitudinal axis of said intermediate support for the passage of a central pin for articulation of the L-shaped members (1, 2); - two curved elongated holes (20, 21) in the shape of arcs of a circle to receive the second pair of pins (13, 14) of the L-shaped members (1, 2), characterized in that the intermediate support comprises - two straight elongated holes (18,19) parallel to the elongated hole, along which are capable to slide the first pair of pins (13',14') of the L-shaped members (1,2), and in that each of the substantially L-shaped members (1,2) comprises: - respective pairs of pins (13, 13'), (14, 14') which pass through respective straight and curved elongated holes (20, 18) and (21, 19) of the L-shaped members (1, 2), in that the central pin for articulation of the two L-shaped members (1,2) with each other passes through the inside of the elongated hole in the intermediate support, and further in that both the centre and the radius of the arc of circle of the curved elongated holes (20,21) in the shape of arcs of a circle, are such that they permit the adjustment of the adjustable clamp so that points of attack (22,23) of the L-shaped members (1,2) of the clamp on said profile sections (28,29) are displaced on a straight line parallel to the longitudinal axis of the intermediate support, in order to permit the adjustment of the adjustable clamp so that the points of attack (22,23) of the L-shaped members (1,2) of the adjustable clamp on said profile sections (28,29), for different widths of these latter, remain parallel with respect to the face of the intermediate support on which the aforesaid profile sections (28,29) bear. the intermediate support comprises: - an elongated hole perpendicular to a longitudinal axis of said intermediate support for the passage of a central pin for articulation of the L-shaped members (1, 2); - two curved elongated holes (20, 21) in the shape of arcs of a circle to receive the second pair of pins (13, 14) of the L-shaped members (1, 2), characterized in that the intermediate support comprises - two straight elongated holes (18,19) parallel to the elongated hole, along which are capable to slide the first pair of pins (13',14') of the L-shaped members (1,2), and in that each of the substantially L-shaped members (1,2) comprises: - respective pairs of pins (13, 13'), (14, 14') which pass through respective straight and curved elongated holes (20, 18) and (21, 19) of the L-shaped members (1, 2), in that the central pin for articulation of the two L-shaped members (1,2) with each other passes through the inside of the elongated hole in the intermediate support, and further in that both the centre and the radius of the arc of circle of the curved elongated holes (20,21) in the shape of arcs of a circle, are such that they permit the adjustment of the adjustable clamp so that points of attack (22,23) of the L-shaped members (1,2) of the clamp on said profile sections (28,29) are displaced on a straight line parallel to the longitudinal axis of the intermediate support, in order to permit the adjustment of the adjustable clamp so that the points of attack (22,23) of the L-shaped members (1,2) of the adjustable clamp on said profile sections (28,29), for different widths of these latter, remain parallel with respect to the face of the intermediate support on which the aforesaid profile sections (28,29) bear. - an elongated hole perpendicular to a longitudinal axis of said intermediate support for the passage of a central pin for articulation of the L-shaped members (1, 2); - two curved elongated holes (20, 21) in the shape of arcs of a circle to receive the second pair of pins (13, 14) of the L-shaped members (1, 2), characterized in that the intermediate support comprises - two straight elongated holes (18,19) parallel to the elongated hole, along which are capable to slide the first pair of pins (13',14') of the L-shaped members (1,2), and in that each of the substantially L-shaped members (1,2) comprises: - respective pairs of pins (13, 13'), (14, 14') which pass through respective straight and curved elongated holes (20, 18) and (21, 19) of the L-shaped members (1, 2), in that the central pin for articulation of the two L-shaped members (1,2) with each other passes through the inside of the elongated hole in the intermediate support, and further in that both the centre and the radius of the arc of circle of the curved elongated holes (20,21) in the shape of arcs of a circle, are such that they permit the adjustment of the adjustable clamp so that points of attack (22,23) of the L-shaped members (1,2) of the clamp on said profile sections (28,29) are displaced on a straight line parallel to the longitudinal axis of the intermediate support, in order to permit the adjustment of the adjustable clamp so that the points of attack (22,23) of the L-shaped members (1,2) of the adjustable clamp on said profile sections (28,29), for different widths of these latter, remain parallel with respect to the face of the intermediate support on which the aforesaid profile sections (28,29) bear.