The show, which saw the contestants perform two songs - one by Take That, the other an Elton John classic - was down by around 740k on last week's instalment.
The latest edition of I'm A Celebrity followed with 8.43m (37.8%) between 9.45pm and 10.45pm.
ITV2's spinoff shows The Xtra Factor and I'm A Celebrity, Get Me Out Of Here Now! managed 608k (2.9%) and 620k (4.6%) at 9.45pm and 10.45pm respectively.
Before X Factor on ITV1, You've Been Framed and Harry Hill's TV Burp took 4.96m (20.6%) and 6.65m (26.4%) in the 7pm hour.
On BBC One, the latest episode of Merlin put in 5.16m (24.3%) at 6.05pm, then a double elimination brought in 9.02m (36.2%) to Strictly Come Dancing between 6.50pm and 8.25pm.
The Lottery draw was seen by 4.55m (17.4%), then a new episode of Casualty followed with 4.36m (17.1%) at 8.35pm.
The final episode of documentary Berlin picked up 1.08m (4.1%) for BBC Two at 8pm, then opinion piece Why Beauty Matters appealed to 750k (3%). An extended version of Have I Got News For You followed with 1.42m (6.4%) at 10pm.
NCIS started Five's night with 667k (2.6%) at 7.35pm, then CSI: NY and CSI put in 763k (3%) and 1.33m (5.6%). Law & Order: SVU interested 1.06m (5.8%) at 10.25pm, then another episode of CSI: NY averaged 800k (7.9%).
Channel 4's repeat of How To Look Good Naked: Sexy Over 60 delivered just 460k (1.8%) at 7.45pm, then a rerun of Tony Robinson documentary Britain's Real Monarch improved the audience to 840k (3.3%).
ITV1 dominated primetime overall, with an average audience share of 38.1% to BBC One's 24%. BBC Two was third with 4%, followed by Five with 3.9% and Channel 4 with 3.3% (+1: 0.4%).
BARB ratings data supplied by Attentional