The invention relates to a control button (12) for a manually actuated sampling pipette, the button comprising lower and upper parts (24a, 24b), one of which is equipped with a force sensor (31) and the other with an actuating member (30). In the vertical position of the button, in a state not subjected to a force, not only does the member (30) ensure that the upper part is retained axially on the lower part (24a), but these parts also define a circular axially retaining connection (42) therebetween, the circular connection exhibiting an axial clearance (47) configured such that, when a pressure is exerted on an off-centre action zone (102a) by the thumb of an operator, the axial clearance (47) is taken up in this zone (102a), while the connection (42) retains a reaction zone (102b), arranged diametrically opposite the action zone (102a), axially and locally relative to the lower part (24a).