Simon Cowell appears to have lost his pulling power, with new figures showing almost four million viewers departing the X Factor since he was previously on the show four years ago.

The show boss bowed out after the 2010 series to launch a US version, but returned this year with hopes that his comeback would give viewing figures a boost.

However, overnight figures for last night's (September 15) edition show a huge drop compared to the equivalent sixth programme of the series during his previous stint as head judge.

At this stage in 2010, the show drew an average audience of 11.6 million on ITV. Last night on the channel, the sixth edition had 7.9 million viewers - a drop of 3.7 million.

Adding in viewing on ITV's catch-up +1 channel boosts Sunday night's figures to 8.5 million, although the channel did not routinely give out such figures four years ago, making it difficult to compare.

Many had put the decline of the show's fortunes on the departure of Simon and fellow judge Cheryl Fernandez-Versini, but figures since their return suggest they have not lured viewers back.

Last year the sixth edition of the show was more than a million viewers higher at 9.6 million, including +1 viewers. It is also down on 2012 when the same show had an audience of nine million, again including the viewers of the catch-up programme.

However, there was some comfort for ITV bosses from last night as the programme was almost a million up on the Sunday edition a week earlier, which had an average audience of 7.6 million, although that show had competition from rival programme Strictly Come Dancing when they had a head-to-head clash.