A label feeder unit associated with a machine for packing tobacco products holds a stack of labels placed in a channel presenting an infeed end, and an outfeed end from which the labels are released to a take-up station, then picked up singly and transferred to a further unit of the machine. The outfeed end of the channel incorporates a transfer mechanism comprising a pair of contrarotating rollers placed on either side of the channel at a distance less than the width of the stack in such a way as to intercept the labels and transfer them to the take-up station, which is movable relative to the outfeed end of the channel under the pressure transmitted to the station by the labels taken up between the rollers. The transfer mechanism forms part of a feedback control loop by which the pressure registering through the labels at the take-up station is kept within prescribed limits.