A spokesperson for the ITV contest confirmed that Brucknell's performance of 'Sweet Dreams (Are Made Of This)' by Eurythmics on Saturday's Halloween special had been given a "robotic effect", but denied using pitch-perfecting Auto-Tune software.
"The X Factor does not use Auto-Tuning," the representative said. "Kitty's track had a retro electronic style, so a robotic effect was used so that the vocals were in keeping with the track.
"This did not alter the pitch or tone of the vocals in any way. If Kitty had hit a wrong note viewers would have heard it. This is nothing like Auto-Tuning and we do not use any effects which would materially change or mislead viewers as to the pitch or tone of the original vocal. It was a robotic-echo effect in line with the track."
However, an insider speculated that the admission may not be enough to appease sceptical viewers after the Auto-Tune scandal that hit last year's series.
X Factor fans hit out at the use of Auto-Tune to improve the vocals of contestants such as Gamu Nhengu in the first audition programme of the 2010 edition. Producers vowed that they would not use voice manipulation on the show again.
"Given the furore over the Auto-Tune scandal, the fact that someone gave the green light to alter the vocal in any way whatsoever - regardless if it was to make it better or not - is unbelievably stupid and naive to say the least," they told The Mirror.
"Millions of viewers are turning off the show and this trickery smacks of a way to make people sit up and take notice again - but it's backfired horribly."
ITV director of entertainment Elaine Bedell last week hit out at the "ludicrous" criticism directed at The X Factor this year.
View pictures of last night's X Factor below: