Reckitt Benckiser lost 1.2 per cent to £67.63 after Church & Dwight, the maker of Arm & Hammer toothpaste and Oxiclean detergent, denied receiving any takeover approaches.
Church was responding to a report that Reckitt was poised to offer $23bn for its US peer.
Analysts saw Henkel of Germany as by far the more likely bidder for Church, given Reckitt would face regulatory concerns about its effective global monopoly for condoms and has been targeting over-the-counter medicines rather than household brands.