The June 1 episode - in which the 46-year-old ITV star wore a daring dress, slashed to the navel - attracted some 663 complaints, the watchdog said.
It received almost twice as many as Comic Relief, in second place.
The fundraising show, broadcast on BBC1 on March 24, attracted 340 complaints for "crude language" and "sexual references".
Emmerdale's March 6 episode was rated third most controversial moment, with 275 complaints for violence and a storyline involving intimidation towards character Aaron Dingle in prison.
Good Morning Britain's interview with ex-English Defence League leader Tommy Robinson, broadcast on June 20, attracted 181 complaints, while ITV comedy Benidorm received 137 for its May 3 episode due to "perceived derogatory reference to a person with a cleft lip".
The figures, up to and including August 10, were released under Freedom of Information laws.
The watchdog routinely publishes details of its complaints.