The glamour model's attempt at completing the series of school-themed challenges during yesterday's 90-minute jungle instalment was seen by 8.02m (32%) from 8.30pm and 10pm.
The fourth episode of the series continued the downward ratings trend. The first episode logged 9.39m (36.2%) on Sunday and has lost a portion of viewers each day.
Tribute show Celebrating The Carpenters pulled in 5.76m (25.9%) for ITV in the hour before Celeb, while over on BBC One, Waterloo Road logged 4.44m (18.8%) between 8pm and 9pm.
Spooks then held strong with 4.63m (18.2%), slightly up on last week's 4.5m (19%).
BBC Two's Top Gear repeat in the 8pm hour interested 2.15m (9.1%), before Andrew Marr's The Making Of Modern Britain drew 2.45m (9.6%).
The Family on Channel 4 managed 1.11m (4.4%) from 9pm, then True Blood was seen by 1.08m (6.4%).
Britain's Best Brain, fronted by Jamie Theakston and Zoe Ball, averaged 522k (2.2%) and Swordfish, the channel's feature film of the evening took 939k (4.3%).
Overall, ITV1 dominated primetime with an average share of 26.9% to BBC One's 18.9%. BBC Two was third with 8.4%, followed by Channel 4 with 5.3% (+1: 0.7%) and Five's 3.2%.
ITV2's episode of Gossip Girl, meanwhile, was seen by 25k (0.1%) at 8.30pm.