The ad, which was broadcast during the first ad break at the end of the show at around 9.45pm, promoted a News of the World offer from the previous week of £5 off when shoppers spend over £30 at supermarket Morrisons.
However, the ad originally scheduled to air showcased editorial content in Sunday's (1 November) edition of the News of the World.
A spokesman for ITV said: "WCRS supplied ITV with incorrect copy. ITV ran the ad supplied by WCRS."
It is thought that ad slots during X Factor could fetch as much as £100,000 each as it reaches its series finale later this year.
ITV's media buying agency is WPP-owned Mindshare, which coincidentally also handles News International's media.
News International, Mindshare and WCRS declined to comment.
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