A labelling machine for applying labels onto containers having a longitudinal axis, a neck on its top, defining an opening, and a base portion with an annular area having the longitudinal axis of the container, the annular area being radially external and defining a resting surface of relative bottle, and a central area surrounded by said annular area, said labelling machine comprising a carousel, comprising: - a plurality of operative units uniformly distributed about the rotation axis of the carousel and mounted at a peripheral portion of the carousel, and adapted to receive a relative container to be labelled and provided with a support element for supporting a base portion of said container; - a horizontal rotating table for transferring said operative unit along a predetermined path from a feeding station of said containers to an outlet station of the containers, the operative units being fixed to said horizontal rotating table and extending coaxially through respective through-holes of said rotating table, and on both sides thereof; and - feeding means for providing at least one label to be applied onto the container borne by said operative unit: wherein said operative unit further comprises an electric motor borne by said conveyor device on the opposite side of said support element with respect to the receiving position of said container and fixed to said support element, and which can be selectively actuated to rotate said support element about an axis transversal to said path, and wherein said support element has a through-opening coaxial to said axis, characterised in that said operative unit also comprises an actuator element coupled to a piston of a fluidic actuator assembly, mounted axially sliding within a through-hole (32, 27c) of said motor means, and displacement means (34, 43, 44) arranged on the opposite side of said motor means with respect to said support element for displacing said actuator element along said axis so as to act, through said opening, on said central area of said container and displace it from a first deformed configuration, in which said central area, is normally arranged in a first configuration at a distance from said neck along axis which is smaller than the distance between neck and said annular area, swollen towards said support element, to a second configuration, in which said central area is centrally retracted inwardly of the container, i.e. arranged at a smaller distance along axis D from neck with respect to the first configuration, and sensor means comprising a position transducer adapted to detect the position of said piston and generating a signal correlated to the position taken by said piston indicating a position difference before and at the end of the interaction stroke with the base portion of relative container, thereby determining the extent of the displacement of said piston, wherein the operative unit is adapted to monitor the displacement of the piston during every action on the containers, thereby detecting the measured displacement difference from a range of desired values for indirect quality control of bottle during displacement of said base portion from said first deformed configuration to the second, inwardly retracted configuration. - a plurality of operative units uniformly distributed about the rotation axis of the carousel and mounted at a peripheral portion of the carousel, and adapted to receive a relative container to be labelled and provided with a support element for supporting a base portion of said container; - a horizontal rotating table for transferring said operative unit along a predetermined path from a feeding station of said containers to an outlet station of the containers, the operative units being fixed to said horizontal rotating table and extending coaxially through respective through-holes of said rotating table, and on both sides thereof; and - feeding means for providing at least one label to be applied onto the container borne by said operative unit: wherein said operative unit further comprises an electric motor borne by said conveyor device on the opposite side of said support element with respect to the receiving position of said container and fixed to said support element, and which can be selectively actuated to rotate said support element about an axis transversal to said path, and wherein said support element has a through-opening coaxial to said axis,